Math Problem Statement

You begin the game Roll and Win by picking a number. Then you roll two regular dice, each numbered 1 through 6, and add the numbers that come up together. If the sum is the number you chose, you win a point. What is the sample space for this game, and how can the probabilities of certain sums be calculated?

Solution

Let's analyze the problem in the image step by step.

Game Description:

You are playing a game called "Roll and Win" where you:

  1. Pick a number.
  2. Roll two regular dice (each numbered 1 through 6).
  3. Add the numbers that come up on the dice.
  4. If the sum equals the number you picked, you win a point.

For example, if you choose 11 and roll a 6 and a 5, you win because 6 + 5 = 11.


Part (a): Sample Space

The sample space is the set of all possible outcomes when rolling two dice. Since each die has 6 faces, the total number of possible outcomes is: 6×6=366 \times 6 = 36 The sample space is the set of all pairs (i, j), where ii is the outcome on die 1 and jj is the outcome on die 2. The sums of the two dice range from 22 (when both dice show 1) to 1212 (when both dice show 6).


Part (b): Outcome Table

To analyze the outcomes, you can create a table with sums of the dice. For each combination of the two dice, the sum is calculated. Below is an example table of possible sums:

123456
1234567
2345678
3456789
45678910
567891011
6789101112

Notice that certain sums, like 7, appear more frequently than others, such as 2 or 12. Each pair (i, j) is equally likely, but not all sums are equally likely because there are more ways to make some sums than others.


Part (c): Probability of Specific Events

  • P(even)P(\text{even}): Probability of rolling an even sum.
  • P(10)P(10): Probability of rolling a sum of 10.
  • P(15)P(15): Probability of rolling a sum of 15.

Even Sums:

The even sums from rolling two dice are: 2,4,6,8,10,122, 4, 6, 8, 10, 12.

Now, let's count how many ways each sum can occur:

  • 2 occurs 1 time: (1,1)
  • 4 occurs 3 times: (1,3), (2,2), (3,1)
  • 6 occurs 5 times: (1,5), (2,4), (3,3), (4,2), (5,1)
  • 8 occurs 5 times: (2,6), (3,5), (4,4), (5,3), (6,2)
  • 10 occurs 3 times: (4,6), (5,5), (6,4)
  • 12 occurs 1 time: (6,6)

So, there are 1+3+5+5+3+1=181 + 3 + 5 + 5 + 3 + 1 = 18 even sums. The probability of an even sum is: P(even)=1836=12P(\text{even}) = \frac{18}{36} = \frac{1}{2}

Sum of 10:

As seen in the table, the sum of 10 can occur in 3 ways: (4,6), (5,5), and (6,4). So, the probability is: P(10)=336=112P(10) = \frac{3}{36} = \frac{1}{12}

Sum of 15:

There is no way to roll a sum of 15 with two dice, so: P(15)=0P(15) = 0


Part (d): Most Likely Sum

The most likely sum is 7, as it occurs the most frequently (6 times) in the table:

  • (1,6)
  • (2,5)
  • (3,4)
  • (4,3)
  • (5,2)
  • (6,1)

The probability of rolling a sum of 7 is: P(7)=636=16P(7) = \frac{6}{36} = \frac{1}{6}


Would you like more details on any of the parts or further explanation?


Here are 5 related questions for practice:

  1. What is the probability of rolling a sum of 2 or 12?
  2. What is the probability of rolling an odd sum?
  3. How many different ways can you roll a sum of 8?
  4. If you roll the dice twice, what is the probability of getting a sum of 6 both times?
  5. How would the probabilities change if you used dice numbered from 1 to 8?

Tip: When working with probabilities in dice games, always count the total number of possible outcomes to build your probability fraction.

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Math Problem Analysis

Mathematical Concepts

Probability
Sample Space
Dice Rolling
Addition of Numbers

Formulas

Total outcomes = 6 * 6 = 36
P(event) = Number of favorable outcomes / Total outcomes

Theorems

Basic probability principles

Suitable Grade Level

Grades 7-10