Question

A and b are two stations, a train goes from a to b at 64 km/hr. And return to a at a slower speed. If its average speed for the whole journey is 56 km/hr. At what speed did it return ?

Answer 1

Answer:

• avg=a+b/2

Explanation:

• 56=64+b/2
• 64+b=112
• b=112-64
• 48kmph

Answer 2

Answer:

Let the required speed be y km/hr.

Then, ( 2 x 64 ) x [ y / (64 + y)] = 56

⇒ 128y = 64 x 56 + 56y

∴ y= (64 x 56 ) / 72

= 49.77 km/hr.