Question

If the speeds of A and B, who start walking in opposite directions on a circular ground, is 9 km/h and 27km/h respectively, and the length of the circular ground is 2400 m; then find after how much time they will meet.
1. 240 seconds
2. 180 seconds
3. 220 seconds
4. 120 seconds

Answer 1

Correct Answer - Option 1 : 240 seconds

Given:

Speed of A = 9 km/h = 9 × (5/18) = 2.5 m/s

Speed of B = 27 km/h = 27 × (5/18) = 7.5 m/s

Formula Used:

Time = Distance/Speed

When two bodies are moving in opposite directions, their relative speed = sum of individual speeds

Calculation:

Relative speed between A and B = 7.5 + 2.5 = 10 m/s

∴ Time taken by them to meet each other = 2400/10 = 240 seconds

When two bodies travel in the opposite directions, the resulting speed is the sum of their individual speeds. Candidate should be careful not to subtract the individual speeds, which is done when the bodies are moving in the same direction.