A person save 5 min: in covering a certain distance by increasing his speed by 20%. The time taken to cover the distance at his usual speed is

Given:

A person saves 5 minutes by increasing his speed by 20%.

Formula used:

Let the usual time taken to cover the distance be T minutes.

Time = Distance / Speed

New speed = Usual speed × 1.2

New time = Usual time - 5

From the relation of time and speed:

(Usual speed) × (Usual time) = (New speed) × (New time)

Calculation:

Let the usual time be T:

(Speed × T) = (1.2 × Speed) × (T - 5)

⇒ T = 1.2 × (T - 5)

⇒ T = 1.2T - 6

⇒ 0.2T = 6

⇒ T = 6 / 0.2

⇒ T = 30 minutes

∴ The correct answer is option (3).