SOLUTION: The wheel of a truck is making 280 rpm. Find the speed of the automobile in kilometers per hour if the radius of the wheel is 0.9m.

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Question 1191874: The wheel of a truck is making 280 rpm. Find the speed of the automobile in kilometers per hour if the radius of the wheel is 0.9m.
Answer by Theo(13342) (Show Source):
You can put this solution on YOUR website!
the radius of the wheel is .9 meters.
the circumference of the wheel is 2 * pi * r = 2 * pi * .9 = 1.8 * pi meters.
that's equal to 1 revolution of the wheel.
multiply that by 280 and you get 504 * pi meters in one minute.
a kilometer is equal to .001 * 1 meter.
504 * pi meters is equal to .001 * 504 * pi meters which is equal to .504 * pi kilometers.
since pi = 3.141592654 then .504 * pi kilometers is equal to 1.583362697 kilometers.
that's in 1 minute.
multiply that by 60 to get 95.00176184 kilometers per hour.
that should be your answer.
fyi:
since 1 kilometer is equal to 0.621371 miles, then the truck is traveling at 59.03133976 miles per hour.
this is not an unreasonable speed.