An automobile has 20-inch diameter wheels. if the wheels revolved three times after the brakes were applied, the stopping distance was approximately

If the automobile's wheels is 20 inch in diameter. We can compute the circumference by:
Circumference = π* diameter
= 3.14159265359 * 20 inches
≈ 188.5 inches

To get the answer in feet, convert inches to feet:
= 188.5 / 12 ft
= 15.7 ft

The answer is 15.7 ft