How many revolutions will a car wheel of diameter 26 inches make as the car travels a distance of seven miles?
sadly i can't solve it
1. The circumference of the wheel is
$\displaystyle c = \pi \cdot d~\implies~c=26\pi\ ''$
2. Convert the 7 miles into inches. (I'm not used to inches, miles, etc. so I used a calculator. But better check this value!)
$\displaystyle 7\ mi = 443520\ ''$
3. To determine how often 7 miles contain the circumference of the wheel you have to divide:
$\displaystyle r = \dfrac{443520\ ''}{26\pi\ ''} \approx 5429.9\ revolutions$