Question

The tires on Eric's car have a diameter of 18 inches. Rounded to the nearest whole number, how many rotations per second does each tire

make when Eric is driving at a rate of 88 feet per second?


A.) 2
B.) 19
C.) 37
D.) 59

Answer 1

Explanation:

We need to figure out how far Eric's car takes him in 1 rotation based on the diameter of his tire in feet. If the diameter of the tire is 18", then it is 1.5'. The circumference will tell us the distance 1 rotation of his tires will take him:

C = 3.1415(1.5) so

C = 4.71225 feet is how far he goes in 1 rotation. If he travels 88 feet in 1 second, we can figure the number of rotations by dividing 88 by 4.71225 to give us the unit rate (or, rotations per second his car makes). This quotient is 18.67 feet per sec, which rounds to 19, choice B.