Question

Pairs of markings a set distance apart are made on highways so that police can detect drivers exceeding the speed limit. over a fixed? distance, the speed r varies inversely with the time t. in one particular pair of? markings, r is 66 mph when t is 66 seconds. find the speed of a car that travels the given distance in 55 seconds.

Answer 1

R  = k / t    where r = speed, t = time and k is a constant
Given r = 66 when t = 66  so we have 
66 = k / 66
so k = 66^2 =  4356

so when t = 55 
speed r =  4356 / 55   =  79.2 mph