Number Trick - Numberphile 

I noticed there was a scum going on with your numbers when i saw 22 responding to 77, which made me realise that your numbers werent random after that point.

That was such an awesome, yet simple trick. If you don't explain it to someone, they'll be impressed because they won't know how you did it.

I went to try this, and the person said 8,888. And I said 1,111. Then they knew these weren't random, and she wasn't impressed.

I knew this trick but never understood it, this guy made me understand it and have fun

I have a tip for you and for all those who are performing this. If your spectator's number has two or more same digits like (7721) it is kind of suspucious for you to write 2278. But in order to make it u suspicious you could for example substract 1000 from your number and write 1278. And then in the next step you add that 1000 to your number. You dont even have to add/sub that simple number. You could for example substract 1324 but then you just must add it to another number. And that's it. Simple tip to make this trick even better. I hope you like it

love it!! great stuff as always :)

My high school friend used to play this trick with me. Today I just find out his trick!

This is the happiest man ever

That's just brilliant XD I wish more people knew how flexible math was

Omg my old math teacher used to do this. He even once wagered his iphone and said if he is wrong he'll give it to the student😂

I like James, he always looks so happy.

I think it would be really awesome to hang out with Brady and James

I'm still at 0:08 and I paused to thumb you up for that amazing English accent!

3:08 "and you can look like a mathematical genius" XD

I watched your some videos and all of them are interesting and full of knowledge. You and your team is awesome! Thanks for great videos.

My dad told me this when i was a kid and that was the most amazing thing to me.

Math doesn't always have to be mind-blowing,you could just sit back and enjoy the fact that numberphiles can always make tricks out of simple arithmetic,which I think is absolutely mind-blowing !

I feel like my Mum is telling me she is not angry, just disappointed!

Quiet brilliant! Love this. Thanks

This is fun - I like starting with a 4-digit number ending in 1 so that the resulting 5-digit sum has even fewer digits in common with the starting one, making the pattern harder to spot!

If someone picked 9999 I'd do something like "oh being cheeky are you going for the biggest - just for that I'm picking 0000, ha ha"and make a little joke of it, etc!

Yes, HTC sent us 100 free phones and a a huge bag of unmarked £100 notes (with non sequential serial numbers) in exchange for showing their product in this video!

I knew how this would go as soon as he said they'll be taking turns now :D

I already came up with this on my own. It’s a pretty easy concept

Sir. you are magician!

I love these videos!! I feel smarter every time I watch one!! :D

That's a funny trick,thank you for explaining it !

This makes me happy!

That was fun and interesting! Thanks for sharing :) 👍👍

In James' defence (this is edited out), he asked if he should add in his head or with calculator, and I said calculator because it just added another prop. Also (you allude to this, but don't agree) I think using the calculator better masks the trick itself, because the columns adding to nine is less likely to be revealed. (I can't claim that was deliberate - as I had not seen the trick before filming - it was all new to me) Calculator also adds a layer of "credibility" for the layman, no?

You, my good sir, are a genius.

SAAMMME!!!! I watched that part 5 times in a row

This guy looks like Fred Weasly

no... I am actually really enjoying myself today! must get back to some editing though...

thanks, hopefully Brady or Dr. James see this question :)

Thks mate , you’re goated

Wow...I watched this a while back and it went right over my head. Now the while back was closer to the time when I suffered a concussion, actually a double concussion. Today I get it...totally simple too! I was having quite a difficult time with simple math...for example, military time is easy to do, sans a tbi. The midnight to noon are as is. The 1300 to 2359 are simple if you take the first two numbers, subtract 2, drop the first number if it's a 1 OR subtract 1 if it's a 2, and that's your hour, now just carry over the minutes. Alternatively, subtract 12, or 2 then 10. I not only couldn't do it, but I couldn't explain it. Ex: 1838 --> 18 - 2 = 16, drop the 1 in the tens place --> 6pm carry over the minutes --> 6:38pm. Ex: 2342 --> 23 - 2 = 21, now subtract 10 = 11, carry over minutes as is 11:42pm. I had expected to join the army and have spent the last several years with calendars and clocks in military time, expecting military time to become second nature...I still have to do the math jog. The math jog was what became second nature until I bumped my noggin!

oh, the math professor doesn't use an iPhone now i truly believe that he's and all-around smart man

this is brilliant

Dr. Grimes Vids are the best

yes, though you need that control number at some point... I think the way James wrote it as an "example off the top of his head" conceals its purpose quite well and made it feel natural!? But the fun of these tricks is adapting them and making them better!

I knew the answer before he added those numbers because I've seen this trick before! All you do is add a 2 to the starting number and subtract 2 from last digit, 3,485 becomes 23,483.

awesome video!

My favorite numberphile mathematican

Some other interesting things may include: If you square a number of ones, you get to count up and down based on how many you used. For example. 1x1 = 1 11x11 = 121 111x111 = 12321 1111x1111 = 1234321 ... ... 111111111x111111111=12345678987654321 And if you square a number ending in 5, you take the extra bit (n), multiply it by n+1, and then put 25 on the end (because the 5 in the ones place is 5x5=25) So for example. 35 x 35. n(3) +1 = 4. n(3) x n+1(4) = 12. So 35 x 35 = 12 (and then put the 25 on the end) 25. 35 x 35 = 1225. Or another example, 75 x 75. 7 + 1 = 8. 7 x 8 = 56 75 x 75 = 5625.

My family know that I’m into math and they can always instantly spot where is the math hidden in the trick. There is no fun with them at all

I remember this trick from when I was a kid!

Oh my god.. This is a trick I learned when I was 8 years old and that I forgot long ago. This is amazing :D

too easy to figure out on the spot I think.

That's Numberwang!

love this!!

A few things about this trick are very obvious: When Brady said 77 and James wrote 22, it completely gave it away. You just had to look at the other numbers and you knew the trick. In the end it's also very obvious that the prediction is so similar to the first number James said. In general the trick isn't very fascinating because logically it is very obvious that you can just outweigh or compensate Brady's numbers with yours.

I did it with my brother and he said 9921 so it became a 2 digit number

What happens if they pick 9886. To get 9 to 9 it's zero and If that's the first number then it's a 3 digit number and it spoils u

It was very easy to catch what you were doing when you picked your numbers.

Act like mathematical genius, James! You are already a genius !

Is that what you're meant to say here? Trada? ... Good to know...

The first number kinda reminds of the famous russian WW2 tank T-34-85... Don't say me that wasn't intentional!

James uses a HTC one!! Truly awesome

Very nice trick!

0:20 left hand Someone's been playing the bass

I was thinking about this problem all day. It would look really suspicious if you were to pick a number starting with zero. The only 2 options I could think of would be to hope that the observer never picks a number with a 9 as a leading digit, of to explicitly state no to choose a number that starts with 9. Glad to see someone else was thinking the same thing.

Your name always gets me

Nice to see you having the HTC One :D

Saw the 9's compliment a mile away.

This trick is gonna get me some serious poon.

It is not expected from your channel. This magic we were used to show in class 4 or 5 in India.

Brilliant mate

Ok, here is importnat part that i feel should be in video. Giving number that add to 9999 can be quite easly spoted but giving one that adds to for exmaple 1027 and next to 1101 isnt so easy. Is little harder to do, but still nothing that you have to make pouse for.

What if the number one chooses happens to be 9999?

Amazing!

I knew those numbers looked suspicious! That's a cool trick!

What if he picked 9999 TWICE?

1+1=2

Nice work

Loved it!

i figured it out at the very bginning... the 77 followed by the 22... just too obvious

If i pick 9999 you can't do it XD

what you meant so say here is BAZINGA !

He is the Steve Irwin of mathematics! He really loves numbers :)

🙏🙏🙏👍

Some of your videos deal with advanced mathematical theory ... and this one isn't one of those. This is 2nd grade elementary school stuff.

I like that this guy is so happy about math...not like my teachers who look suicidal and couldn't care less about our education so long as they get a paycheck.

AWESOME!

This one felt awfully simple, not like Numberphile. Don't like it.

very old boring trick

Your videos are amazing. My students love them (and they're really not the type of students who you'd expect to watch maths videos at all). You've made my students love numbers just by using them in such an entertaining way. Heres me thinking that teaching them maths could never compete in todays world of entertainment, yet you guys have really shown me that it's possible to actually use entertainment to teach maths. Thank you! You need to make revision clips for kids or something. I'd buy them!

Woah!!! Im totally gonna do this, and have a lot of fun freaking out my really dumb friends! Thanks so much!! : D!!!!!!!

I honestly got so excited when I saw he had upgraded from a crappy iPhone to the new and amazing HTC One! =)

With this I can rule the world.

nice, want more of these :)

I figured it out before he added the numbers up. I did a similar trick to win the "Loves me..." multiplayer game in New Super Mario Bros. A flower has like 17 petals and each player can pull between 1 to 3 petals/ turn. Cycles "loves me"/ "loves me not" each time a petal is pulled. The player wins by picking the last petal on a "loves me" flower, or by avoiding, "loves me not". So if you go second you can force the opponent to pick the last flower by removing flowers to a multiple of 4.

This guy is always smiling!

very cool trick

Love it! Thanks :)

I immediately what you were doing when you wrote the 3rd number when the 2nd and 3rd number in my head added up to 9999, as well as the 4th and 5th number.

You just say "ok, this time give me another one straight away"

Oh god, this guy is like sheldon on real life! And I love it!

A mathematician using a phone calculator = Priceless :-)

Chile, I love that place.