Question

A cab has an average speed of 60 km / hr while going from Indore to Ujjain and has an average speed of X km / hr while returning the same distance from Ujjain to Indore. IF the average speed of the cab for the whole journey is 48 km / hr, the value of X is
1. 45 km / hr
2. 40 km / hr
3. 36 km / hr
4. 30 km / hr

Answer 1

Correct Answer - Option 2 : 40 km / hr

Given:

A cab has an average speed of 60 km / hr while going from Indore to Ujjain and has an average speed of X km / hr while returning the same distance from Ujjain to Indore.

If the average speed of the cab for the whole journey is 48 km / hr

Formula used:

Average speed = 2S₁S₂/(S₁ + S₂)

Calculation:

According to the question,

Average speed = 48 km/hr

S₁ = 60 km/hr and S₂ = X

⇒ 48 = (2 × 60 × X)/(60 + X)

⇒ 48 × (60 + X) = 120X

⇒ 60 × 48 = (120 – 48)x

⇒ X = 2880/72

⇒ X = 40 

∴ The value of X is 40 km/hr.