A pick-up truck is fitted with new tires which have a diameter of 42 inches. How fast will the pick-up truck be moving when the wheels are rotating at 280 revolutions per minute? Express the answer in miles per hour rounded to the nearest whole number.

280 revolutions per minute is:

280/60 = 4,66667 revolutions per second.

now we need to calculate perimeter of the tire

O = D*pi = 42*3,1415 = 131.943 inches

Speed of truck is:

V = 4,66667 * 131.943 = 615.73 inches per second.

Now we need to express this in miles per hour.

615,73 * 1,5782*10^ (-5) * 3600

V = 34.984 miles per hour.

after rounding we get

V = 35 miles per hour.