A spinner has equal regions numbered 1 through 21. What is the probability that the spinner will stop on an even number or a multiple of 3?

Answer 1

1 through 21

even numbers are 2,4,6,8,10,12,14,16,18,&20

10 out of 21 are even

numbers divisible by 3 are 3,6,9,12,15,18 & 21

7 out of 21 are divisible by 3

3 of the 7 are also even

(10+7-3)/21 = 14/21 = 2/3

probability of even = 10/21

probability of divisibility by 3 = 7/21 = 1/3

probability of even or divisible by 3 = 2/3

= about 67% chance