College Algebra, Chapter 10, 10.3, Section 10.3, Problem 16

A child's game has a spinner as shown in the figure. Find the probability of the given event.

a.) The spinner stops on an even number.

The even numbers on the spinner are 2,4,6 and 8 which are four numbers. Thus, the probability in this case is

$\displaystyle \frac{4}{9}$

b.) The spinner stops on an odd number or a number greater than 3.

The odd numbers on the spinner are 1,3,5,7 and 9 which are five numbers. The numbers greater than 3 on the spinner are the number 4,5,6,7,8 and 9. Since the numbers 5,7 and 9 are simultaneously odd numbers and greater than 3, the probability of the union of two events is

$\displaystyle \frac{5}{9} + \frac{6}{9} - \frac{3}{9} = \frac{8}{9}$