Rani goes to school from home at a certain speed and returns to home at the speed of 50 km/h. If the distance between her home and school is 20 km and the average speed of the whole journey is 37.5 km/h, then what is her speed from home to school?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 30 km/h.
Let's assume the initial speed S1 is x km/h
If the distance is the same then
Average speed = 2S1S2/(S1 + S2)
37.5 = 2S150/(S1 + 50)
⇒ 37.5S1 + 1875 = 100S1
⇒ S1 = 1875/62.5
⇒ S1 = 30 km/h
x = 30 km/h