Question

a boy covers 10kms at a speed of 5km/hr 30 km/hr at a speed of 7kmph and 20 kms at speed of 15kmph find the average speed?

Answer 1

Distance 1 = 10 km.
Speed 1 = 5 km/h.
Time 1 = Distance 1 / Speed 1.
=10/5 = 2 hours.

Distance 2 = 30 km.
Speed 2 = 7 km/h.
Time 2 = Distance 2 / Speed 2.
=30/7=4.28 hours.

Distance 3 = 20 km.
Speed 3 = 15 km/h.
Time 3 = Distance 3 / Speed 3.
=20/15=1.33 hours.

Average speed = Distance 1 + Distance 2 + Distance 3 / time 1 + time 2 + time 3.
=10+30+20/2+4.28+1.33.
=60/7.61.
=7.88 km/h.

Therefore, the average speed of the boy is 7.88 km/h.