How many revolutions will a car wheel of diameter 30 in make

How many revolutions will a car wheel of diameter 30 in, make over a period of half an hour if the car is traveling at 60 mph?

Circumference=pi*d= 3.14 *30=approx 94

Car spped is 60mph . SO in half hour it travels 60*1/2=30 miles

And 1 mile= 5280 feet

So in 30mile ,it is 158400 feet

And 1 feet =12 inches. Therefore 158400 feet= 1900800 inches

Number of rotations=1900800/94= 20221