Problema Solution
If the speed limit is decreased by 10 km/h on a 100 km stretch of a highway, the trip will take a half hour longer than usual. What is the usual speed limit?
Answer provided by our tutors
Let
v = the usual speed limit, v>=0
v - 10 = decreased speed by 10 km/h
d = 100 km the distance traveled
Since speed = distance/time follows time = distance/speed.
d/(v - 10) = d/v + 0.5
100/(v - 10) = 100/v + 0.5
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click here to see the equation solved for v
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v = 50 km/h
The usual speed limit is 50 km/h.