Correct Answer - Option 2 : 7
Given:
A takes 2 hours 30 minutes more than B to walk 40 km. If A doubles his speed, then he can make it in 1 hour less than B.
Concept Used:
Time = Distance/ Speed
Calculation:
Let, Speed of A is x km/h
Time taken by A to cover the distance 40/x hour
Time taken by B (40/x - 2.5) hours
When A doubles his speed time taken by A 40/2x hour
Accordingly,
[(40/x) – 2.5)] – (40/2x) = 1
⇒ (40/x) – (40/2x) = 3.5
⇒ 40/2x = 7/2
⇒ x = 40/7
Time taken by A to cover the distance 40 ÷ (40/7)
⇒ 7 hours
∴ A needs 7 hours to walk a 40 km distance.