When rolling a pair of dice, the probability of getting a particular total is not very high. For example, the probability of failing to roll a total of 7 is 5 times the probability of successfully rolling a total of 7. The total probability (probability of failing to roll a 7 + probability of successfully rolling a 7) is 1. What is the probability of rolling a 7?
A) 1 in 6
B) 1 in 18
C) 1 in 9
D) None of these.

Question

Quizplus · Accepted Answer

There are 6 possible outcomes when rolling two dice (1+1, 1+2, 1+3, etc. up to 6+6). Out of these, there are 6 ways to roll a total of 7 (1+6, 2+5, 3+4, 4+3, 5+2, and 6+1). The probability of rolling a 7 is therefore 6/36, which simplifies to 1/6. The probability of failing to roll a 7 is 30/36, which simplifies to 5/6. Adding these two probabilities together gives 1, as required. Therefore, the answer is A) 1 in 6.

When Rolling a Pair of Dice, the Probability of Getting