Problema Solution
A bus covered the 400-km distance between points A and B at a certain speed. On the way back the bus traveled at the same speed for 2 hours and then increased the speed by 10 km/hour until it reached A, thus spending 20 fewer minutes on the return trip. How long did the return trip take?
Answer provided by our tutors
Let 'v' the speed of the bus when traveling from A to B.
d = 400 km the distance
400/v = the time of the trip from A to B
400/v - 20/60 = the time of the return trip
Since speed = distance/time follows distance = speed*time.
v*2 + (v + 10)*(400/v - 2 - 20/60) = 400
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click here to see the equation solved for v
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v = 80 km/hr
We need to ignore the solution -150 since the speed can not be negative.
400/80 - 20/60 =14/3 hr = 4 hr 2*60/3 min = 4 hr 40 min
The return trip took 4 hours and 40 minutes.