Fast Mental Multiplication Trick - Multiply in your head using base 20 and 30

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This mental multiplication trick uses the idea of a third number - a base number - to help us multiply two numbers in your head. This series of videos first looks at multiplying numbers near 10 using base 10. The second video looks at multiplying using base 20 and 30. The third video looks at how to apply this mental multiplication trick to numbers near 50. The forth video the investigates ho to easilt mentally multiply numbers near to 100. Continue your mental math multiplication abilties here!
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1 окт 2024

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Комментарии : 664

@Eljulitus 3 года назад

My life would have been a lot different if you were my math teacher at school. Thanks a lot for your lessons!

@Ali-fq3nz 3 года назад

Same here…😊

@1trucxhondamov589 3 года назад

When I went to public school, they taught from a curriculum not research or experience! They were there to get a nice pay check!😃

@davidlewis1680 3 года назад

Yes I agree , I was terrified of my maths teacher . On a Friday afternoon double maths he’d give me homework and would say learn your times tables and on Monday morning for every you get wrong you’ll get the slipper . I hope he’s sat in hell

@Mr_Wiley 6 лет назад

I now feel like a wizard. RU-vid just obliterated all my early years of early math education in less than 30 minutes and 2 videos. I'm buzzing in excitement as an adult.

@no-body-nobody 4 года назад

yess also see 3blue1brown

@charley408 3 года назад

🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯 I know right! My mind is blown, and that's not easy to do!

@charley408 3 года назад

@@no-body-nobody ???

@PurplePassionPaper 3 года назад

Me too!

@ditto1051 3 года назад

Same here!

@katiemorris9711 10 лет назад

Now my day wasn't completely useless.

@matrixfull 5 лет назад

same ^^

@kevinv.5961 5 лет назад

Katie Morris same

@i.am.tavisha.m 4 года назад

same bro ^^^^^

@iwouldliketobelievethattha7561 4 года назад

i misread the name as Kamala Harris lol

@UmarAlFarooq 3 года назад

If you smile at someone, your day will never be useless.

@shriyashaw1430 7 лет назад

I'm not showing this to anyone. I really wanna beat my friend in maths and now I can. MUAHAHAHA.

@giofts7497 4 года назад

Shadow 88 Me Too... MUAAAAHAHAHAHA

@i.am.tavisha.m 4 года назад

me too

@smithblack7939 3 года назад

Your friend already knows the trick . MUAHAHA.

@mrhoneybadger5539 3 года назад

@Jarod David They probably fat after the 2 years.

@GeorgeSPAMTindle 8 лет назад

I am hooked, just love this stuff. I am pleased that there are so many viewers, it's good to see it's not just me then who finds this stuff exciting!

@Khonic23 7 лет назад

Reverend George well yes, there's over 7 billion people on earth and at least 40% have internet access. You're obviously not going to be the only one interested lol

@ianc8398 7 лет назад

Khonic would that be 2.8 billion people interested?????

@bigberthayourbff6255 6 лет назад

But not all 2.8 people who have internet access are interested. Maybe even the people who *dont* have internet access are interested. You never know what goes on in people’s minds.

@vrsce0178 5 лет назад

@@Khonic23 How many people you know that are interested in math or learning in general that go as far to look up videos on YT on math? 😂You know this generation doesnt find interest in actually using the internet to learn

@tecmath 11 лет назад

This technique I studied a few years ago - and many of them I have either known, been shown by colleagues, or funnily enough been shown by students of mine as they try to interpret the simplest method of doing math. Thanks for the question!

@abdullahmunirnouroz2090 6 лет назад

what bse we use to multiply 3 digit numbers and how to do it??

@trensic5716 3 года назад

your students are literally 90000 iq

@64marcovix 3 года назад

25x22 can be done with another method which particularly I find easier though I follow your teaching and it works too. So, to multiply any number by 25 keep in mind 25x 4= 100 That means, if we divide the other multiplicand by 4 we get this: 22÷4 ( to divide by 4 just divide by 2 twice!) Thus, 22÷2=11, now again 11÷2=5.5 X10= 550 our final answer! But mentally you can do it in 2 seconds with practice

@B.editzz 2 года назад

@@trensic5716 ong

@GordieGii 2 года назад

@@abdullahmunirnouroz2090 The first step would be to find the largest multiple of 100 that is lower than both numbers. Let's say the numbers are 254 and 337. 254 = 200+54 and 337 = 200+137 so (200+54) * (200+137) then multiply using FOIL = 200*200 + 200*137 + 54*200 + 54*137 then factor = 200*(200+137+54) + 54*137 = 2*100*391 + 54*137 = 2*39100 + 54*137 = 78200 + 54*137 next use the same trick to multiply 54*137 (you might want to write down the 78200 unless you can memorize it) so 54 = 50+4 and 137 = 50+87 (50+4) * (50*87) = 50*50 + 50*87 + 4*50 + 4*87 hmm. I don't like 4*87, so how about this 54*137 = (54*2) * (137/2) 108*137/2 = (100+8) * (100+37) / 2 = (100*100 + 100*37 + 8*100 + 8*37) / 2 = (100*(145) + 8*37) / 2 = (14500 + 8*30 + 8*7) / 2 = (14500 + 240 + 56) / 2 = 14796 / 2 = 7000+350+45+3 = 7398 +78200 (remember?) = 85598 Tada! Of course 4*87 isn't really that bad so 50*(54+87) + 4*87 = 5*10*141 + 4*87 = 5*1410 + 4*87 = 7050 + 348 = 7398 same as the other way

@saeediearcher7339 5 лет назад

he sounds excited when he talks its so cool

@tonybarfridge4369 4 года назад

saeedie archer maths can be exciting

@hugolevaillant5208 4 года назад

@@tonybarfridge4369 math is exciting

@darpanrajput9651 3 года назад

@@tonybarfridge4369 uUhuio0

@RAIDFIX 10 лет назад

Thanks my friend. I'm nearly 60 and really enjoyed learning a new technique. Will find this very useful. You have a patient teaching style too. Cheers

@supersmasher3619 4 года назад

chopper hello

@krishnavavhal7443 4 года назад

chopper

@jeffayoe7468 Год назад

@@krishnavavhal7443 chopper

@georgigeranov9778 5 лет назад

Goodness gracious! I wish someone had taught me that in my school years... Still it's a good mental exercise. Thousand thanks!

@katmiranda7687 10 лет назад

I FEELL LIKE A MATH MASTER EHEHEHE. Spent 2 hours practicing your method. Thank you. I'm feeling more confident about my mental math now. THANK YOU. I LOVE YOU DUDE.

@legend519 10 лет назад

I'm studying for the PCAT and needed to learn to multiply without a calculator (sadly I've become dependent on them). This video has helped A LOT. Thank you!

@jasperbutcher2596 5 лет назад

100% agree. Hey looking back, I hope you did well!

@liamichellequiroznunez5396 4 года назад

Same!!

@betselotaderaw83 4 года назад

same here man

@Myce 3 года назад

Same. I take it in 2 days. Scored a 75 on my practice test but I have self confidence issues and am uneducated in simple math

@EdwardKure-l9u 9 месяцев назад

Me too😊😊👍

@_sonicfive 3 года назад

Now all I need is an opportunity where multiplying 78 x 56 comes up so I can impress people. Sadly I don't remember a time this was useful besides school.

@educatedonealways6281 3 года назад

If you don't find math useful then you are just dumb or in a dead end career

@chrisnewtownnsw 10 лет назад

Thank you very much for the tips I found this to be pretty fkn amazing and exactly what I needed for poker. You have a qld accent am I right?

@tecmath 10 лет назад

Thanks for the comment!That is the accent of a Victorian who lived a lot of the time in the NT.

@hamishblack4480 7 лет назад

WA all the way

@MrHazza187 7 лет назад

@_unknown_3768 6 лет назад

Hi 👋 I am 14 and this September I am going into year 10 and I’m always getting nervous coz I felt like I might fail math but omg I stumbled across your channel and honestly I am so grateful I have you teach me better than my teachers and I can do it at my own speed I have learnt things in less than 1 hour . I have subscribed to you , your amazing and I can’t wait to watch more videos this helps me a lot ! 😊

@ryanfrancisco179 5 лет назад

I have never calculated in my head faster than today. I am forever changed for the better.

@zacharyquinn2144 5 лет назад

How would you multiply numbers that are far apart, ex like 34 × 7

@abdelmahamnmoodally7398 5 лет назад

For me I would just do 30x7 then 7x4 and add the answers. There’s probably an easier way tho

@falucy 5 лет назад

Who’s watching in 2o19? O.O

@purpleontop2133 5 лет назад

ⱣɨnkȺđøɍȺƀłɇFøxɏ me

@michaelfrance7849 4 года назад

Hello 2020😂

@MichaelKeaveneyYouTube 8 лет назад

Your IQ is ∞×∞. Seriously, I'm considered a genius and you actually teach me things I don't know yet. You're Einstein.

@thenextshenanigantownandth4393 6 лет назад

Every since I was young iv'e had massive phobia of maths, due to my dyscalculia. Your videos were a massive help, thanks.

@tecmath 11 лет назад

Thanks for commenting - this happens in the next part video - base level 50!

@godiseverything1482 4 года назад

Can you do a video on functions? I would appreciate it. You make Math seem so easy.. Thank you

@nathandaniel5451 10 лет назад

Thank you, this will help me alot since i am in grade 8. On the side I done: 19 x 26 = 494 32 x 27 = 864 43 x 37 = 1,591 52 x 38 = 1,976 64 x 71 = 4,544 106 x 98 = 10,388 43 x 51 = 2193 13 x 8 = 104 512 x 497 = 254,464

@gmwire1935 10 лет назад

good for you

@MyBigThing2010 7 лет назад

On a side note, I've* done... On a side note, I have* done... On a side note, I *did do these/this.... On a side note, I have also completed....(Best choice.) Now pay attention in English class (punctuation and grammar) and you'll be good to go!

@michaelempeigne3519 7 лет назад

I am amazed that you did these and got them all right including some which were not covered in the video such as 106 x 98

@bcnicholas123 7 лет назад

this is gonna help so much in finance, thank you

@PrideofPitchers 6 лет назад

Go Tigers!

@StarFury2 11 лет назад

It's cool, but only works where two numbers are close together. Try 14 x 89 for example... whatever base you pick, there is a lot of calculation to do after it.

@jamesmacgregor2838 10 лет назад

Your channel is amazing! After years of getting by with minimal basic math skills I decided to make some changes. Your channel is an inspiration. You make learning so much more enjoyable and natural. Now I'm getting into physics and algebra and I'm loving it! If you had told me 2 days ago that I would be multiplying double digits in my head I would have told you that you were crazy! Awesome job!

@jamespaul4618 2 года назад

Your insights and techniques regarding mental math and multiplication are greatly appreciated. This is very empowering. Thanks for sharing these concepts.

@joechiou8888 4 года назад

Very interesting! (X+A)*(X+B)= X^2+(A+B)X+AB=((X+A)+B)*X+AB, very smart!!! Very smart way to use algebra!!

@EzkPalacio 8 лет назад

Thank you SO much, you are an amazing person. I learned so much more in TWO days of watching your videos than I did in the 4 years of high school!!! I'm definitely subscribing. Your accent makes the videos much more entertaining! Once again, thank you.

@212Michael 4 года назад

25 x 23? I would look at that and go 25 x 20 would be 25 x 2 add a 0 = 500. That leaves you with 25 x 3 = 75 and then 500 + 75 = 575.

@earlhaywood4372 3 года назад

He speaks with a strong mumbling accent quite hurriedly in a very soft tone. Although it's sounds phonetically pleasant , but for someone unfirmailiar it's a little difficult to follow. I am sure his intentions are quite good .

@ends.paradox 3 года назад

I know you made this a long time ago, but I struggle with mental math and multiplication, so I completely avoided it because it made me feel so stupid. Thank you so much for helping me, these tricks are super helpful! wish I knew about you when I was younger :)

@Catski0 7 лет назад

for 25x anything, surely it's easier to just divide the number by 4 then x100? e.g. 25*22 => 22/4 = 5.5, *100 =550.

@bebopshoobop 4 года назад

Watching these because Im taking the medical school admissions test, which doesn’t allow calculators. Now I’m wondering why i haven’t done this years ago.

@healthsignalllc3456 4 года назад

Thank you sooooo much! I love it plus when having to be patient (like waiting in line) I like to make up numbers and do them in my head. I’m looking to get real fast at it. Thank you again!

@banniemccormick4971 6 лет назад

I just wanted to thank you for posting these videos....I have never been so fast at math before!!! Thank you so much for sharing your wisdom!!!

@jovanakostencova1813 4 года назад

How do i do stuff like 78× 39?!

@sidekicks1403 3 года назад

25*23 can be done this way: 25*23=25*25-50=625-50=575 this is based on the X5 * X5 trick so its not a very generalized trick but its really easy to use when its applicable

@tomalcolm 3 года назад

This is great. I’ve always done something like this for easy numbers by rounding and then adding or subtracting the difference, but this is more efficient with fewer steps, and I can do it with less simple numbers.

@argenis7323 9 лет назад

this is a really interesting metod, very usefull thanks a lot.....

@LENUS2 5 лет назад

Unbelievable. Perfect method. Thanks. Liked, Subscribed

@freakymundo 8 лет назад

I prefer doing it this way: if you have 33*27 , u have a +3 and a -3 , cz u are in base 30 , the answer will be: (900) + ((+3 -3)*30) + (-9) . => 900 + 0 - 9 = 891 other case: If u have 25 * 22 then u have +5 and +2 => (400) + (5+2)*20) + (5*2) => 400 + (7*20) + 10 = 550 other case: if u have 32 * 27 then u have +2 and -3 => 900 + ((2-3)*30) + (-6) = 864 => 900 -30 - 6 = 864

@dominiccharles6987 4 года назад

he's got a nice way of speaking and a soothing voice. thanks a lot.

@aztecwarrior1421 5 лет назад

I am 64 and enjoying this stuff. Thank you sir!

@jandemant7812 3 года назад

4:42 I wouls multiply 20*28 and then subtract the extra 1*28 in my head . All numbers close to 10 20 30 or whatever can be calculated like that. But calculation always depends of the specific calculation and to the knowledge of the person trying to solve it. I was lucky to have a math teacher wit, both great skills in knowledge and great skills in getting the message through. i think most of us in class loved math. He made it so interesting, so many ways to deal with numbers. It has been a great hel pall my life, being able to calculate. We got taught a lot i newer use, like ( a+b)(a-b)= and (a+b). It was in the 70`in Denmark.

@armandk7036 3 года назад

damn, I waste my time doing long math in the past. Awesome video

@kellycrites80 3 года назад

This is so helpful to not only myself but my middle schooler since he has been virtual schooling since March 2020. Along with your other videos you have made helping him with math so much easier. Cheers!

@eepohce 5 лет назад

I cannot stop watching this series. This should definitely be taught. I couldn't imagine doing 2 digit number multiplication in my head before this yet it's so simple. Well done.

@ekoi1995 10 лет назад

hmmm (10n+a)(10n+b)=10n[(10n+a)+b]+ab

@djnAbNo2 10 лет назад

Nice, I derived it for just numbers in base 10, but you generalised it for any base!

@antonysachs1966 6 лет назад

good stuff. Trying to work through 'why this works". Appreciate your thoughts.

@epitomeofaqueen 9 лет назад

So weird. I tried to do a base 20 problem before you wrote yours and mine was 25x22! So close to yours. Anyhow, let me finish watching this. I have to train some tutors and I know this will be awesome to help them.

@kinnaripatel2872 3 года назад

Can't understand him... Using captions, but he's speaking wayyyy too fast. 🙄 Lol

@zacharyquinn2144 5 лет назад

So much easier than long multiplication 😂😂

@WingedShell82 5 лет назад

Honestly, I'm having so much fun with this lmao instead of doing hw

@jedics1 3 года назад

In less than an hour this channel made me better at maths than a decade of it at school did....Im probably still going to use my phone though because it doesn't make silly mistakes like me :)

@jinalgandhi1809 3 года назад

Pl show how to multiple 62*54 using this trick I am.not getting proper answer...awating ur revert .

@lordMaroza 5 лет назад

Hot damn.... Why hasn't YT recommended this earlier when I actually had more brain power to learn it quicker.... Thank you so much, nevertheless!

@treygillott2212 4 года назад

you're literally getting me ready for my aptitude test for the navy. love your vids chief

@aliciad4283 5 лет назад

Brilliant! I am so thankful. Finally a way to simply and quickly do math that is conceptual and leads to mental math!

@ashirwadgrcharoonrashid3907 5 лет назад

I am from India, I enjoyed your way of teaching very much

@sylverwing 3 года назад

This is pretty cool but why does it work? Where can I find the logic behind this witchcraft!

@Cr_goat007 3 года назад

Thanks for helping know my teacher will be surprised about it

@AmienHashim 9 лет назад

yo your the best man thx!!!!!!! -----____-----

@사라-t9g 6 лет назад

It's a little confusing..I hope I can get my mind to do this stuff quickly some time

@dmr778810 5 лет назад

For the equation example of 26 x 35 (answered at 7:45), I decided to test my luck and try to see if I could figure it out using base 30. I was so happy when I actually got it.

@LigerDJ217 8 лет назад

ok so i maybe in year 11 right now and i am starting to see my grades drop when i study alot, so i started to search how i can improve my maths and when i found your videos and started to watch them it made my mind start up again. so i thank you for helping me change my studying habbits for when i have my final full year exam some time at the end of the year. Your Examples really help my mind think like it was in primary school. Thanks TecMath

@timeforamazingchest5271 5 лет назад

This will be a huge help for day-to-day stuff. Thanks a lot!

@idreesismail591 4 года назад

I've been watching you for long time and your videos are perfect mate thanks keep up the good work👌

@gianttrance5180 3 года назад

Why am I learning math from Brian Houston?

@HungNguyen-dl9nl 3 года назад

Love this video. I been doing the long way in my head. Now you just help me to do multiplication in my head way faster. 👍

@angelonocable__-1377 7 лет назад

Excuse me but how do you think deep in this subject of multiplying do you try and find all sorts of ways that it may work, did this subject take a long time to realize how to do it in your mind was this passed on to you because clearly I don't get how you adapted this trick?

@MyBigThing2010 7 лет назад

Angelo Blanco it's not so much a trick. More that of education and a different way to get to the same destination. If you spend time in college you learn many ways to do the same thing.

@camiloparra4659 10 лет назад

Great post, keep them coming! Had quick question: What if two numbers fall in different bases? e.g: 35 x 73 ? What suggestions do you have? Would love to see how you approach this

@eXiLeMercury 10 лет назад

What I would do is just break it down. Really thats (35x10)7 + 35 x 3 which is alot easier to work with. 350 x 7 in simpler form is 35 x 7 35 x 7 in simpler form is 35 x 5 (add a 0 and divide by 2=175) + 70 = 245. Add the 0 we left off of 350 = 2450 Then just add 35 x 3 (105) to 2450 and you get 2555 35 x 73 = 2555

@bigberthayourbff6255 6 лет назад

Damn you’re a grown man, you should know this

@loveleebelle 5 лет назад

How about using base 50???

@GrimRawr 3 года назад

I love that he gets right to the important parts of the information. I feel like Khan academy had all these extra thoughts.

@Ganbakodon 2 года назад

Lol how am I supposed to work out 6 x 15 while also trying to calculate 26 x 35 at 7:40

@Mr99deepak 10 лет назад

you are superb!! hat's off boss!!

@malcolmoliver7678 9 лет назад

Omg! I am in love with this technique. I totally plan to use this strategy for my GMAT! Thanks again man!

@iwouldliketobelievethattha7561 4 года назад

Good Luck!

@GordieGii 2 года назад

How would you use this method for 97*19? 0r 85*14, 73*21, 67*28, 59*13 or 41*17? It seems this method is only useful for about 10% of two by two digit multiplication problems.

@МамаВ-ц9г 2 года назад

Sorry. My English is bad 🤷‍♀️ But you intrigued me. I tried 73x21. For the base I took both 20 and 70. The result is the same. Only with base 20 it is easer and faster to count 🤗

@GordieGii 2 года назад

@@МамаВ-ц9г Not my point. Of course you get the same answer either way. My point is that this method is supposed to save time over traditional multiplication, and I don't think it saves much, if any, time unless both numbers are close to the same base.

@МамаВ-ц9г 2 года назад

@@GordieGii 🤗 Thank you. I from a different point of view - arouse the child’s interest in mathematics. I need to check time - I wondered.

@connorking984 6 лет назад

Dang, I've always been good at mental maths, I developed my own method and I'm probably the best at it of anyone I know personally but this is probably faster given some practice refining this. Awesome, looking forward to learning more!

@dannie3117 3 года назад

I am really enjoying getting back into math without a calculator. Thank you

@keylonjoseph7348 3 года назад

What happens when someone eats 100 cheese a day? Answer: They burst FartZillar

@zombaxi1812 3 года назад

I am so glad I found this. I'm 11

@dustinp2932 4 года назад

Even though some of you found this new method of multiplying it's really only useful when numbers are close to each other

@dippykumar 11 лет назад

what about 48x62?

@ringochia8572 10 лет назад

-12 2 48 x 62 = 3000 - 24 = 2976

@dianabuck7310 8 лет назад

This is great! I can definitely do this. :D I don't know if my students will get it, but I might try as an enrichment exercise.

@SungazerDNB 10 лет назад

Thank you so much, I actually get all this! I sucked at math in school because fear got the better of me.

@gayleciaralee 7 лет назад

Thanks for helping me I am doing long multiplication in Grade four and why did you start videos?Is that explain everything?

@njn2704 4 года назад

23*75? 34*58? 56*78? 87*41? etc...😕

@tomascancelliere4348 2 года назад

Base 10 should have been taught when i was in grade school. I am 43, this is not only easier but it teaches kids to use their brain in a more complex way, spacial memory is what i like to call it. Visualizing numbers in your head and holding them as a place value without writing it down step by step is how it should be done in my opinion, then only writing it on paper or calculator to check your answer. I think its a great brain exercise to help strengthen those neural connections at an early age

@mskellytolar 4 года назад

Mr. Tech Math man's voice is so dreamy :-)

@Patriot41776 6 лет назад

These are amazing. Thank you so much. Wish I knew this 20+ years ago FFS! Well done sir and g’day to you!

@johnwjr7 4 года назад

On some of them, you don't need to do all that. For example the 3rd to last example (25x22). A faster way to do ones like this would be just adding 500+50. The 500 coming from 25x20 and the 50 from 25x2. On one like 30x19, you would do 30x20 (600) minus 30 (because you only need 19 30's, not 20) to get your answer of 570. At least the ones like this are faster for me to do. You can do them all this way, but his way is faster on some of them.

@yuvix7960 7 лет назад

Omggg,thankssssssss ALOT!

@divermike8943 2 месяца назад

12:32 This is diagonal multiplication. What is harder to do in your head is multiplying two digit numbers that are not near a convenient reference number (base). 76×78 for instance. You can do it but there are more calculations to keep tract of. I used a ref of 70. 6 +78 = 84 , 840×7 = 5600+ 28 = 5880, 5880 + 6(8)=5880+48 = 5928. That's a lot to keep track of in your head IMHO. You could use a reference of 100 but now you have to also multiply 14 x12 in your head. Another diagonal multiplication. 12:32

@HarrisonEkeblad 4 года назад

You're an absolute legend, thanks for this.

@GordieGii 2 года назад

This is how it works: 23 * 22 (first step: 23=20+3 and 22=20+2 therefore) = (20+3) * (20+2) ( next we multiply using FOIL) = 20*20 + 3*20 + 20*2 + 3*2 = 20*(20+3+2) + 3*2 (then factor) = 20*(25) + 3*2 (second step: 23+2=25) = (2*10)*25 + 3*2 (next a little juggling) = 2*(10*25) + 3*2 = 2*250 + 3*2 (third step: add a zero and double) = 500+6 (finally: multiply the discrepancies and add) = 506 And that's how you do algebra in your head.

@buzzwerd8093 10 лет назад

I had to go back to algebra because set in my ways to see what you're doing. Wow that's a nice rearrangement of binomials!

@ringochia8572 10 лет назад

24 x 25 = 600 04 05 24 x 25 1) Add 5 to 24 then multiply by 20 or to make it easier, multiply by 2 first then 10. So u'll get something like this: 2(24 + 5)[10] = 2(29) x 10 = 58 x 10 = 580. 2) See the numbers 04 & 05? You multiply these 2 numbers to get 20. 3) Add 20 to 580 & you'll get 600. Q: "Why multiply 2? In base 10, there is no multiplying by 2." A: "You need to multiply it by 2 because it's base 20." Q: "Why multiply 10?" A: "It's 24 x 25 not 4 x 5. LOL! Definitely, your answer is in 100. Not 1 or 10." I'll help if you need help. I believe everybody who understands this will help those who wouldn't.

@stingerzgamer792 7 лет назад

I’m showing this to my teacher 😂

@ORANGE-ct6wj 7 лет назад

me to

@goodboythings7343 5 лет назад

You dont just have to use a base thats a multiple of 10. You can use any number, just follow the same method. 10(x-10+y)+(x-10)(y-10)=x*y b=10 b(x+y-b)+(x-b)(y-b)=x*y -b^2+bx+by+xy-bx-by+b^2=x*y bx^2-bx-bx+by-by+xy=x*y xy=x*y

@yksharma5288 6 лет назад

Sir thanks you so much

@PeachyNanaUK 3 года назад

Aged 68 I’ve learnt how to multiply large numbers in my head. Yay. Was always able to multiply up to 12 x 12 in my head and some other easy ones but this is great!