Math Problem Statement

How many ways can a sum of 6 be obtained when three dice are rolled?

Solution

The problem asks how many ways a sum of 6 can be obtained when rolling three dice.

Each die has 6 faces, so we need to find the number of combinations of rolling three dice that give a total sum of 6.

Step-by-step approach:

  1. The minimum value on each die is 1. Therefore, to get a sum of 6, we could explore all combinations where the sum of the three numbers on the dice equals 6.

  2. We are looking for solutions to the equation: x1+x2+x3=6x_1 + x_2 + x_3 = 6 where x1,x2,x3x_1, x_2, x_3 are integers between 1 and 6 (since each die can show values from 1 to 6).

  3. We can subtract 1 from each xix_i to simplify the problem to finding non-negative integers y1,y2,y3y_1, y_2, y_3 such that: y1+y2+y3=3y_1 + y_2 + y_3 = 3 where each yi0y_i \geq 0. This is a typical stars and bars problem, with the number of solutions given by the binomial coefficient (3+22)=(52)=10\binom{3+2}{2} = \binom{5}{2} = 10.

  4. Now, we enumerate the specific dice rolls that result in a sum of 6:

    • (1, 1, 4)
    • (1, 2, 3)
    • (1, 3, 2)
    • (1, 4, 1)
    • (2, 1, 3)
    • (2, 2, 2)
    • (2, 3, 1)
    • (3, 1, 2)
    • (3, 2, 1)
    • (4, 1, 1)

There are 10 ways to obtain a sum of 6 with three dice.

Would you like more details on this, or do you have any further questions?

Related Questions:

  1. How many ways can a sum of 7 be obtained with three dice?
  2. What is the probability of getting a sum of 6 when rolling three dice?
  3. How many ways can a sum of 8 be obtained with three dice?
  4. What is the expected sum when rolling three dice?
  5. How does the distribution of sums from rolling three dice look?

Tip:

For problems involving dice rolls, breaking the problem down into small cases or using combinatorial methods like stars and bars is often very effective.

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Math Problem Analysis

Mathematical Concepts

Combinatorics
Probability
Stars and Bars Method

Formulas

x1 + x2 + x3 = 6
y1 + y2 + y3 = 3 (stars and bars)

Theorems

Stars and Bars Theorem

Suitable Grade Level

Grades 8-10