Question

Correct answers only please!

If you have changed the tires on your car, the original diameter is 24.5 inches. to a new diameter of 26 inches, how fast are you actually going if your speedometer is reading 53 mph?

A. 50.5 mph

B. 53 mph

C. 56.2 mph

D. 62.8 mph

Answer 1

c. 56.2 mph

Explanation:

In most cars, the speedometer reading is proportional to tire rotation speed, so a larger diameter tire will go farther for the same number of rotations. That is, the distance traveled in a certain length of time is proportional to the tire circumference, which is proportional to the tire diameter.

The car with new tires will actually be going at the speed of ...

(26 in)/(24.5 in) × (53 mi/h) ≈ 56.245 mi/h ≈ 56.2 mph