Problema Solution
Two cars leave towns 800 kilometers apart at the same time and travel toward each other. One car's rate is 18 kilometers per hour less than the other's. If they meet in 4 hours, what is the rate of the slower car?
Do not do any rounding.
Answer provided by our tutors
let
v1 = the rate of the faster car
v2 = the rate of the slower car, v2 < v1
t = 4 h the time of the travel
One car's rate is 18 kilometers per hour less than the other's
v1 = v2 + 18
since the distance between the cars was 800 km at the beginning after the 4 hour the sum of the distances of the two cars will be 800
we will use the fact that distance = speed*time
v1*t + v2*t = 800
v1*4 + v2*4 = 800
plug v1 = v2 + 18 into the last equation
(v2 + 18)*4 + v2*4 = 800
by solving we find
v2 = 91 km/h
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the rate of the slower car is 91 kilometers per hour.