Honors PreCalculus
posted by Anonymous .
It is known that when a car with wheels of radius 14 in. is driven at 35 mph, the wheels turn at an approximate rate of 420 revoulutions for minute. Show how to obtain this rate of turn.
If you ride a bicycle a distance of 5 miles in 15 minutes at a constant speed and if the bicycle's wheels have diameter 27 in., find the wheels approximate rate of turn (in revoultions per minute)
Can someone at least help me get started even if you cannot answer the question completely. Thanks

THe wheel has to cover 5 miles, right? So divide the 5miles by the wheel circumference to get the number of turns, and then divide by time.

Can you or someone else please clarify your explanation. Thank you.

What part of Mr. Pursley's explanation don't you understand? He's given you these steps:
Divide the 5 miles by the wheel circumference. That gives you the number of turns.
Divide the number of turns by the time. 
I understand what he's telling me to do, but I've gone through it multiple times and it just doesn't seem correct.

What answer did you get?

If I understand the steps correctly, 27x 3.14= 84.78 divided by 5= 16.956 divided by 15= 1.1304 (which seems pretty slow) If you notice a mistake I have made in the procedure please let me know. Thanks

number of turns=5miles/(27inches*PI)
Now, you have to convert miles to inches to divide this out.
Then, after you get revolutions from the above, divide by 15 min to get rev/min 
Thank you I appreciate all the help.