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.