A car completes a journey at an average speed of 40km/h.At what speed must it travel on the return journey if the average speed

Question

GrogVix [38]

3 years ago

11

A car completes a journey at an average speed of 40km/h.At what speed must it travel on the return journey if the average speed

for the complete journey is 60km/h?

Mathematics

1 answer:

nalin [4] · Answer 1 · 2022-06-04T04:02:06+03:00

The distance, s = 40t₁ where t₁ is the time to complete the outward journey.
The same distance = vt₂ where t₂ is the time to complete the return journey at speed v.
For the whole journey, 2s=60(t₁+t₂). Therefore s=30(t₁+t₂)=40t₁=vt₂.
30t₁+30t₂=40t₁, 10t₁=30t₂, t₁=3t₂, so s=120t₂=vt₂ and v=120kph.