Dice problems agaaaain

What is the probability of getting a sum of 10 when rolling three fair six-sided dice?

Image credit: Wikipedia Jynus
1 9 \frac{1}{9} 1 6 \frac{1}{6} 1 12 \frac{1}{12} 1 8 \frac{1}{8}

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7 solutions

Bill Bell
Oct 7, 2014

The possible outcomes of a single die can be represented using the polynomial: x + x 2 + x 3 + x 4 + x 5 + x 6 x+{ x }^{ 2 }+{ x }^{ 3 }+{ x }^{ 4 }+{ x }^{ 5 }+{ x }^{ 6 }

Then the possible outcomes of three dice is representable as the third power of this polynomial:

x 18 + 3 x 17 + 6 x 16 + 10 x 15 + 15 x 14 + 21 x 13 + 25 x 12 + 27 x 11 + 27 x 10 + 25 x 9 + 21 x 8 + 15 x 7 + 10 x 6 + 6 x 5 + 3 x 4 + x 3 x^{18} + 3 x^{17} + 6 x^{16} + 10 x^{15} + 15 x^{14} + 21 x^{13} + 25 x^{12} + 27 x^{11} + 27 x^{10} + 25 x^{9} + 21 x^{8} + 15 x^{7} + 10 x^{6} + 6 x^{5} + 3 x^{4} + x^{3}

There's one way of getting 18, there are three ways of getting 17, and so on. The total number of ways the dice can appear is the sum of the coefficients, 216. There are 27 ways of getting 10.

This is by multinomial theorem, right ?

Parth Dhar - 6 years, 8 months ago

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It should be something like an OGF

Lorenzo Correale - 6 years, 8 months ago

My apologies for the delay in responding.

See http://www.whitman.edu/mathematics/cgt_online/section03.01.html. As Mr Coreale suggests these are generating functions; they are based on Newton's binomial theorem.

Bill Bell - 6 years, 8 months ago

The possible combinations of 3 3 integers, each between 1 1 and 6 6 inclusive, which sum to 10, along with the number of possible permutations, are as follows:

(i) 1 , 3 , 6 6 1, 3, 6 \Longrightarrow 6 permutations,

(ii) 1 , 4 , 5 6 1, 4, 5 \Longrightarrow 6 permutations,

(iii) 2 , 2 , 6 3 2, 2, 6 \Longrightarrow 3 permutations,

(iv) 2 , 3 , 5 6 2, 3, 5 \Longrightarrow 6 permutations,

(v) 2 , 4 , 4 3 2, 4, 4 \Longrightarrow 3 permutations,

(vi) 3 , 3 , 4 3 3, 3, 4 \Longrightarrow 3 permutations.

This gives us a total of 27 27 outcomes out of the 6 3 = 216 6^{3} = 216 outcomes that can occur without restrictions. Thus the desired probability is 27 216 = 1 8 \frac{27}{216} = \boxed{\frac{1}{8}} .

Yatish Pathak
Oct 10, 2014

Here is the list of permutation for getting a total of 10
6 3 1 == 6
6 2 2 == 3
5 4 1 == 6
5 3 2 == 6
4 4 2 == 3
4 3 3 == 3
Total == 27
So, Required probability = 27/216 = 1/8



Edir García
Oct 9, 2014

Just count the permutations pivoting on one die when it's 1 the other two ought to be 9 there are 4/36 permutations for this.

when it's 2 the other two ought to be 8 - 5/36 permutations

when it's 3 the other two ought to be 7 - 6/36 permutations

when it's 4 the other two ought to be 6 - 5/36 permutations

when it's 5 the other two ought to be 5 - 4/36 permutations

when it's 6 the other two ought to be 4 - 3/36 permutations

By probability multiplication rule and the fact that on the pivoted dice each number has 1/6 to roll. we multiply all of the other two dice probabilities times 1/6 and then add up 27/216 = 1/8

Carry Chancing
Nov 18, 2016

Di ak maaram. Chamba la adto

Rohendra Kumar
Jul 15, 2015

guesss..........any easier methods plz.....

Sigmund Dela Cruz
Mar 30, 2015

event is 27 and sample space is 6^3 so P= 27/6^3 or 1/8 which is the answer XD

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