Question

A lottery game has balls numbered 1 through 15. What is the probability of selecting an even numbered ball or a 13?A. 2/5B. 8/15C. 7/15D. 7/8

Answer 1

We will be using the following formula:

P(even or 13) = P(even) + P(13)

a.) How many even are there in 1 through 15?

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15

There are 7 even numbers.

Thus,

P(even) = 7/15

b.) What is P(13)?

Since there is only one 13 number in the set,

P(13) = 1/15

We get,

$\text{ P(even or 13) = P(even) + P(13)}$$\text{ P(even or 13) = }\frac{\text{ 7}}{\text{ 15}}\text{ + }\frac{\text{ 1}}{\text{ 15}}\text{ }$$\text{ = }\frac{\text{ 8}}{\text{ 15}}$$\text{ P(even or 13) = }\frac{\text{ 8}}{\text{ 15}}$

Therefore, the answer is letter B - 8/15