Fast Math Trick - How to multiply numbers under twenty faster than a calculator! 

I teach many people labelled slow learners. Keep practicing, although sometimes a different explanation can help. Good luck!

i was told i was dyslexic at 27 and have never been able to understand maths till i found your videos which has helped me a lot so thank you!

There are different videos on different length digits. These are listed in my channel. More material will be released later this year (i'm on holiday at the moment).

I answered them faster than other kids in class,and they were like,WHAT how did you do that so fast😀

cannot thank you enough! I am slowly becoming numerate for the first time in my 29 years on this earth thanks to your videos!

You are by far, the greatest most intelligent Math Professor in the Universe! Thank You so much for helping me get back into College. I aspire to become a Teacher as inspirational and driven to teach as you are Sir, thank you so much again.

the blokes a legend ... always smiling when i listen to him....

Keep in mind that multiplication is a combination of addition as well and as the numbers get larger there are combinations of subtraction addition multiplication can become a factor as well.

Sure - I have another video that does this...see my channel!

I've got other videos showing how to deal with numbers over 20.

Man your videos are awesome so simple and easy and love how you show the work to the problems , step by step plz keep them coming

Really appreciate your content. I always wanted to know the trick behind quick mental math

You can put that into an equation, which can be simplified to this :P : The base number in, for example, 12*14 is 10. Num1 means how far from the base number is the first number (2). Num2 means how far from the base number is the second number (4). (base^2) + (base * num1) + (base * num2) + (num1 * num2) (10^2) + (10 * 2) + (10 * 4) + (2 * 4) 100 + 20 + 40 + 8 = 168

this channels helping me so much I have my SATs soon and we've been doing practice tests and all my correct answers are basically because of this channel XD

Great videos, I fly for an airline and we use mental math for a lot of things, this will help me to be faster and more accurate at calculations... much appreciated

Omg. I can now do this quick smart. Its like being given a sharp needle after having used a blunt needle for years. THANK YOU SO MUCH!

For numbers between 10 and 20: The general idea is this: We have (10+a) * (10+b) We then add the units of any number, to the whole of the other number. As is mentioned in the video, it doesn't matter which way you do this, as both will give you (10+a+b). Since this is actually the value of the 10s, we should multiply this whole expression by 10 to get 100+10a+10b. For the units, we multiply the units from the two original numbers to get ab. This is then added to 100+10a+10b to get 100+10a+10b+ab. This of course makes perfect sense if you simply expand the brackets of the original expression: (10+a)*(10+b) = (10*10) + a*10 + 10*b + a*b = 100+10a+10b+ab. But this only really works for numbers between 10 and 20, as mentioned. What if we tried doing it with larger 2-digit numbers? For 54 x 73, the numbers are 44 and 63 away from 10 respectively. We then add 44 to 73 (or 54 to 63) to get 117. We then treat this as the "10s", so we'd treat this at 1170. We'd then multiply the 44 and 63. This is then done the same method: Subtract 10 from both numbers to get 34 and 53. Add 44 + 53 (or 34 + 63) to get 97. This is also the 10s part, so we'd treat this as 970. We then have to multiply the 34 x 53. Repeat the above to get 24 and 43 as the distances from 10. Add 34 + 43 or 24 + 53 to get 87. This is also the 10s part, so this is 770. Then multiply 24 x 43. To do this, again, we add 14 + 43 or 24 + 33 to get 57. This is again the 10s part, so that would be 570 Now we have to multiply 24 x 43. Again, we have 14 + 43, or 24 + 33 to get 67. This is actually 670. Now we're left with 14 x 33. 33 + 4 = 37 (or 23 + 14 = 37) .. we treat this as 370. Now we just have 4 x 23 This is equal to 92. Now what happens if we add everything up? 1170 0970 0770 0570 0370 0092 0002 0440 2500 1000 3942 ... which is the actual answer. Of course, this is far too much work, since we have a chain of constantly multiplying 2 digit numbers, going down by 10 each time.

Thank you Techmath, I've learnt so much from you. :)

I have just found your channel and very interesting it is too. Although retired now, this quick maths is still of interest .. at least it'll keep my brain active. What's more, I'll be able to keep an eye on what my wife spends .. on yet another new handbag 🤣

"It's a little trick that only you me and rest of the RU-vid will know about" Hmm..yeah it's a top secret😂😂😂

Dear Ocarina: Go to 5:50 he said: 9+17=26 . You can do 9+17 or 7+19 , both will give the same answer which is 26, then you multiply 7by9 to get 63, then you add 260+63= 323. watch again please, to get clear. Thanks

If I knew this guy in my first year of college....

If the numbers are under twenty - I treat it a bit differently - say for 7 x 18, the tens number is the single digit number (7 ie 70), the unit number is 7x8 = 56. 70 + 56 = 126.

pretty cool! just showed this to my granddaughter in the second grade having math problems and she was thrilled!

"that'll put the wind right up 'em" - haha gotta love an Aussie maths teacher

This whole channel is like arming school kids to take down their maths teachers and I LOVE IT

I used to be bad at year 9 maths but since I watched 2 of your videos I became a master thank you

hello from usa, thanks

Dear sir, actually i am not getting understand your language, but i can see your trick.. Hats off... You are the fabulous

It is going to get really interesting when the teacher tells you to "show your work".

Love your methods, thanks for sharing

I'm happy with that :) Thanks!

woooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooow! Thank you so much!

HOLY CRAP after watching this i did my own sum and wrote it down and i'm like that can't be the answer way to easy but it was.. thanks man from tassie :P

Man. You never ever disappoint me in the least bit. I've learned so much from your channel in the last few years now.. Great, Great Teaching. Wow!-:)) I'm not so intimidated by math anymore.............😁😉🙂

Thanks for tutorial, you help me improve my mental sums. My basic time table needs refreshing.

you have shown the easiest way to solve the regular hard problem. thank U so much.

I have watched two videos this one and multiplication with 11 and believe me it is awesome....... I really loved your method.... amazing

This really helps! I don't feel so intimidiatted anymore. Thank you ;)

this is a very smart way of showing students much easier and faster it has been avery helpful way to learn i love it this way thank you

You are a credit to humanity.

Omg Man, you helped me a lot, thanks dude!

I love this channel!

Thank you so much! You made me like math even more!

You're so awesome!! Thanks a lot! :D Have a great day, sir!!!!

Over 20 it's possible to do it, but is more complicated. The exact expression is: (first number + second number -10) *10 + (first number -10) * (second number -10) and it's needed to be more time. For example: 36*27 = (36+17)*10+26*17 = 530+(26+7)*10+16*7 = 530+330+112 = 972 36*55 = (36+45)*10+26*45 = 810+(26+35)*10+16*35 = 810+610+(16+25)*10+6*25 = 1420+410+150 = 1980

"Fish are friends, not food" -Bruce the Shark

omg thats awsome now maths is a littel bit easy

Bless this man.

Thank you Sir! i was a weak at math when i was schooling. didn't score more than 50. anyway i managed to pass the O/L exam really hard. to be honest, math made me hate it. however, now i love learning math by myself.

great and amazing thank you for sharing your idea

I love how he mentioned when your in class next, haha I'm 36 and watching all these vids, very helpful 👌

This is amazing! Do you have an app to practice this on I could download?

Your a miracle... Why weren't you around in my high school days

Thanks mate I'm doing my tests in school and this really helped me out:)

Can this channel be monetized? Love your vids

this is so help full

Very impressive! I really feel you are talking to and teaching me! Personally! Very good teacher!

what about for instance; 36*27 ? What would the steps for that be?

I like your first method much better!!

Thank you teacher

en.m.wikipedia.org/wiki/Trachtenberg_system Here is the extended system. There was a book in the 1960s that explained it all, and the life of Trachtenberg, which was a case a great determination through very extreme adversity. I am pleased you are introducing his methods to a new generation: an antidote to the electronic calculator! :)

you are genius boss

I really want to hug you for this!!!! Thank you so muuuuccchhhh!!!!!!!

mind blowing ........ superbbbb se b uparrrr

Love you mate.

wow and before I thought I was good at times tables but now..... THANKS !!!

Awesome trick!

Much love from Canada.

Thank you so much best technique ever❤❤❤❤❤❤❤❤❤❤❤

g'day and welcome to tecmeth

Very good method.thanku sir.

Thank you so much!!

You're a genuis! Feels like my life has been saved.

I love that it easy thank you for helping me

Your so amazing,Thank you.

Another great video thanks a million times

These are awesome! Thanks for help.

Liked your channel. Its awesome. Great work.

THANKS SO MUCH!!!!

I LUV your Awesome multiply

Nice job although I love a good calculator,you don't need one all of the time. Thanks

Thank you thank you.

this makes so much sense!!!!!!!!!!!!!

Thank you so much

THIS IS REALLY USEFUL, THANKS A LOOOOTTT

At around 3:15 you could also add 1+2+1+4, and you get 8. I just figured that out :D

Even faster way, is understanding the near 10's and addition subtraction 17 x19 = (17 x 20) - 17 children are good with upto 5 multipliers in table, things get's with bigger numbers there after so, 17 x 20 = 340 - 17 = 340 -10 - 7 = 323.

awesome mate!

thanks,this heps me a lot

really help ful!!!

thanks very much

I freaking love these

i just watched this video and was doing it the same way you said at the end from the start :D

Or 12 × 14 Now, Firstly, Add 12 to 4 i.e.12+4=16 Secondly, Multiply second digits i.e. 2×4=8 So the answer will be 168

what if it be numbers like 73 and 62

Your a saviour!

thank you so much

Or... 13X12 10X10 (always the 100 so just put 1 down) 1 3+2 = 5 15 3X2=6 156

only me , you and the rest of youtube :) lol