CPM Homework Help : MC2 Problem 9-111

A box contains $15$ yellow, $15$ orange, and $15$ green tennis balls. If Izzy draws a tennis ball at random out of the box, what is the probability that he drew either a green or an orange tennis ball? Show your work and express your answer as a percent.

Hint:

$\text{Probability }= \frac{\text{number of tennis balls we're looking for}}{\text{Total number of tennis balls}}$

Help:

How many green and orange tennis balls are there?
How many total tennis balls are there?

Step 1:

$15$ green $+ 15$ orange $= 30$ green or orange tennis balls.
$15$ green $+ 15$ orange $+ 15$ yellow = 45 total tennis balls.

Step 2:

$\frac{30}{45} \text{ Now convert this fraction to a percent.}$

Answer:

$66 \frac{2}{3}$