Problema Solution
Pairs of markings a set distance a part 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 45 mph when T is 9 seconds. Find the speed of a car that travels the given distance in 8 seconds.
Answer provided by our tutors
y varies inversely with x (or "x and y are inversely proportional") if there is a constant k such that:
y = k/x
yx = k, where k is constant
let 'v' represent the speed of the car that travels the given distance in 8 seconds:
45*9 = x*8
by solving we find:
x = 50.625 mph
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the speed of the car that travels the given distance in 8 seconds is 50.625 mph.