Question

A student calculates that the circumference of a tire with a rim diameter of 15 inches and a sidewall width of 4.6 inches is 61.8 inches by doing the following calculation:(15+4.6)xpi. Explain the error. (Show problem set up. Provide appropriate units)

Answer 1

The error was on the diameter. The tire diameter was supposed to be;

4.6+15+4.6=24.2

The student only includes one sidewall width

Explanation:

The question is on circumerence of a tire

Here we apply the formulae for circumference of a circle

C=2
`\pi`×r or
`\pi` × d where r is the radius of the tire and d is the diameter

Finding d= diameter of rim + sidewall to the right +sidewall to the left

d= 15+4.6+4.6=24.2 inches

r=d/2= 12.1

C=2 ×
`\pi`×r

C=2×3.14×12.1 =75.99 Inches