Three Dice Trick - Numberphile

Show me what's up that ladder hobbit boy

7 (the top and bottom of a die) + pre-reroll dice + a rerolled die. So simply add 7 to last three dice? Got it.

This is fantastic! It is the first time I have seen any of your videos. I'm a 66 year old retired school teacher. You are a brilliant teacher - clear, concise and very interesting to listen to. Your manner, style and presentation are so very engaging. This would be fantastic for teachers to use in the classroom with their students - and the students can then go home and enjoy fooling their parents. Thank you so very much for bringing us this video. I just subscribed.

Now divide by zero.

you could JUST have them roll 3 dice PREDICT that total, WITHOUT ANY additional adding or turning dice over........WITH NORMAL dice.

@Numberphile watching your video it occurred to me that you could have them "repeat the stage where you add the bottom of the dice and roll it again" many times, just add +7 for every re-roll.
However at the pub it may become increasingly difficult to count how many re-rolls!

The only opposite side sun for things such as a d12 or d20 is always the number of faces + 1

Great video

These trucks are so disappointing because of the inelgance of needing to know the opposite number. All hes doing is adding 7 to the totals he sees. I dont really see this as a trick. I could make this trick with 5 die rerolling 3 with the same rules and it would be the same trick. Theres not a satisfying reveal because the trick asks for so much information before it even starts

I was confused originally thinking the idea was to tell which dice was rerolled but that is only possible to get 100% right if they are unique in the end, not to tell you the number they arrived at, phew. I suppose that is one way to extend the trick, force reroll until they are unique then you tell them which 1 of the 3 got rerolled.

hi bro plz help me I am in loss

but why does it work?

"I'm impressed that you are impressed" best quote ever

You talked tae my class on Monday, and will be doing it again emmrow

F*cking gorgeous

Cool!

I paused the video and solved it successfully. Felt amazing 😂😂

Hi Numberphile team,

We can do the same trick with two dice also.

Very nice trick.

SEEING ISNT BELIEVING THE REAL TRUTH IS WHAT IS IT THAT YOU BELIEVE YOUR SEEING.....

the sum of the opposite faces of any evenly distributed die is the biggest number on the die +1. I mean it's not hard to pick two random opposite faces and add them up, but this is nice and easy and elegant, it's similar to Gauß's idea with the 1+20, 2+19, 3+18, ...

Is the real Adam Savage a supporter?

can you make an 8-sided dice have the same sum on all opposite faces? or for some reason is it impossible?

my 8dies have opposite faces...

I believe some dice have numbers arranged so that the carved out part to display the number impacts the roll minimally. i.e. the carved out numbers aren't creating an unfair die.

Great stuff. To really misdirect people, the person doing the trick should, after working out the number, reroll the dice, then pretend to think for a moment, and then call out the number.

Numberphile is going downhill

I'm impressed + that you're impressed = meta-impressive lies in the spacetime between (lol).

Now should swap in a non-standard 6 sided die to mess with the magician. Where the opposite sides don't equal 7

Easy if you know that the numbers on opposite faces add up to 7. So you're turning the first value of the dice that you re-roll into a 7 and the result is just the sum of the 3 dice at the end plus 7.

have a class roll 1000 dice, reroll 777, add 5439 to number showing?

I'll bring a dice with 1, 2 and 3 on the opposite side of the 4, 5 and 6, "magician".

Dudes! Did you know that 2+5=7?! Wow!

Methinks this trick would have added levels of complexity if cubic, dodecahedral and icosahedral dies were commingled together in such a performance -- would seem to make it more challenging, but not impossible (?) to work out the math(s)

eww wtf so lame

very cheap trick! lol!!!!

I can tell by the dice that our man plays DnD

Here before he explains it. I figured it out. YES.

If you put the middle step at the end you won't have to ask what happened. Can't believe this guy is so slow 😂

I instantly figured 7 would be related somehow but I couldn't figure out why - much like the guy filming it, hah.

In love with every Ben Sparks video because Ben Sparks

The problem with trying this trick on people is way too many people will fail to follow the instructions correctly and end up with the wrong mental number, which will make the prediction seem 'wrong'.

I can make this game even much better:
Take n dice
Roll all of them
Do the same process on each die
The answer is sum of the Numbers + 7n 😀

The magic number is always 7

Brilliant!

i knew the 7 thing, most people do, but it was still surprising. because you could choose which to reroll. took me a minute to realize the 7 thing was all that mattered

huh because it was obvious to me from the start... I wonder why