Question

The average speed of a person in driving to school is 30 km/h on the return trip alog the same route the average speed is 25 km/h whiat is the average spped for the round trip to the school?

Answer 1

Let the distance from school to home be x km.
Speed for 1st half of journey=30 km/h.
⇒Time taken for 1st half=$\frac{x}{30}$ hours.
Speed for 2nd half of journey=25 km/h.
⇒Time for 2nd half of journey=$\frac{x}{25}$ hours.
Average speed=Total Distance/Total Time
=$\frac{x+x}{x/30+x/25}$ km/h
=$\frac{2x}{(5x+6x)/150}$ km/h
=$\frac{2x}{11x/150}$ km/h
=$\frac{2x*150}{11x}$ km/h
=$\frac{300}{11}$ km/h
=27 $\frac{3}{11}$ km/h.
Ans:The average speed of the person is 27 $\frac{3}{11}$ km/h.