Question

A train travels from Mumbai to Goa at a speed of 45 km per hour and return to Mumbai at a speed of 36 km per hour what is average speed of the train over the whole journey?

Answer 1

You can use below methods instead of traditional speed = Distance/time method

Method 1:

S1 - speed 1

S2 - speed 2

Considering distance same.

Average speed = 2*S1*S2/(S1+S2)

Average speed = 2*30*50/(30+50)

= 3000/80=37.5

Method 2:

Making ratio 30:50 = 3:5

Difference between speeds = 50 - 30 = 20

Dividing difference by sum of ratios = 20 /8 = 2.5

Taking lowest speed and lowest of ratio

Average speed = 30 + 3 * 2.5 = 37.