Question

Suppose you roll a special 9-sided die. What is the probability that the number rolled is a "7" OR a "8"?Enter you answer as a fraction or a decimal with 3 decimal digits.

Answer 1

A 9-sided die has 9 sides meaning that there are a total of 9 possible outcomes.

We are interested in the outcomes "7" OR a "8"

The probability that the number rolled is a "7" is given by

$P=\frac{number\text{ of favorable outcomes}}{\text{total number of outcomes}}$

There is only 1 favorable outcome which is to roll a "7" and the total number of outcomes are 9.

$P(7)=\frac{1}{9}$

So, the probability that the number rolled is a "7" is 1/9

The probability that the number rolled is a "8" is given by

There is only 1 favorable outcome which is to roll a "8" and the total number of outcomes are 9.

$P(8)=\frac{1}{9}$

So, the probability that the number rolled is a "8" is 1/9

The probability that the number rolled is a "7" OR a "8" is given by

$P(7\; or\; 8)=P(7)+P(8)=\frac{1}{9}+\frac{1}{9}=\frac{2}{9}$

There is a 2/9 probability that the number rolled is a "7" OR a "8".