Wheelchair Rear

Wheelchair Rear
SAT math help?

A wheelchair with a rear wheel with a radius of 18 makes 360 rotations. How many rotations will a wheel with a radius of 4 make simultaneously?

please explain how you solved it!

thanks!

Every rotation is when the circumference of the wheel has been covered. First, calculate the circumference using 18 as the radius = 2pi(18) = 36pi. Now calculate the circumference using 4: 2pi(4) = 8pi. Now, calculate the total distance covered by the 360 rotations = 360 * 36pi = 12960 pi. Divide that by 8 pi and you get 1620 rotations.

Passenger Loading in a Rear Entry Wheelchair Van