Trig
posted by Alli .
Need hellpp!!
If a bicycle has 26 inch diameter wheels and the front “chain”drive has a radius of 2.1 inches and the back drive has a radius of 2.5 inches, how far does the bicycle travel for every one rotation of the cranks (pedals)? Carry out all calculations exactly and round to the nearest inch the final answer only.
and this
A Ford Expedition Eddie Bauer Edition comes standard with 17'' rims (which correspondes to a tire with 25.7'' diameter). Suppose you decide to later upgrade these tires for 19'' rims (corresponding to a tire with 28.2'' diameter). If you do not get your onboard computer reset for the new tires, the odometer will not be accurate. After your tires have actually driven 5000 miles, how many miles will the odometer report the Expedition has been driven? Round to the nearest mile. Use the fact that 1 mi. = 5,280 ft.)
I don't get these at all! Please help.

wouldn't the first be...
2PI*26 (2.5/2.1)?
Then
(19/17)=5000/x
solve for x the computer will underestimate the mileage.