picnic time!
One day you were with your class on a picnic. During return journey from picnic spot to your school, your bus was travelling at the scheduled average speed v1=70 km/h, suddenly, it began to rain so the driver reduced the speed and drove the bus at average speed of v2=60km/h. After the rain stopped, the driver drove at the average speed of v3=75km/h to cover the remaining distance of 40 km and reached in exactly scheduled time. How long did it rain?
( type the number of minutes)
The answer is 16.
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1 solution
Let the scheduled time of journey be t . The the scheduled distance of journey is 70 t .
We just now have to equate total distances covered at different average speeds to this value.
Let time traveled at 70 k m h r − 1 be t 1 , 60 k m h r − 1 be t 2 & 75 k m h r − 1 be t 3
Therefore, 70 k m h r − 1 * t 1 + 60 k m h r − 1 * t 2 + 75 k m h r − 1 * t 3 = 70 t
Clearly t 3 = 32 min.
Also note that t 1 + t 2 + t 3 = t
Solving the equations yields the answer.