The speed of A and B are in the ratio 3 : 4. A takes 20 minutes more than B to reach a destination. Time in which A reach the destination?

Answer: Option A

Ratio of speed = 3 : 4
Ratio of time taken = 4 : 3 (As Speed ∝ $$\frac{1}{\text{Time}},$$   When distance remains constant.)
Let time taken by A and B be 4x and 3x hour respectively.

Then,
4x - 3x = $$\frac{20}{60}$$
Or, x = $$\frac{1}{3}$$
Hence, time taken by A = 4x
hours = 4 × $$\frac{1}{3}$$ = $$1\frac{1}{3}$$ hours.