Question

A man travels from place A to B and comes back. He goes at a speed of 21 kmph and returns at a speed of 14 kmph. Find the average speed for his whole journey.
1. 12.8 kmph
2. 15.8 kmph
3. 16.8 kmph
4. 10.6 kmph

Answer 1

Correct Answer - Option 3 : 16.8 kmph

Given:

A man travels from place A to B and comes back. He goes at a speed of 21 kmph and returns at a speed of 14 kmph.

Formula Used:

When distance is equal, Average speed = 2 S1 × S2 / (S1 + S2)

Calculation:

Average speed for his whole journey =  2 × 21 × 14 / (21 +14)

= 2 × 21 × 14 × 1/35

= 16.8 kmph