Question

A car covers a distance at a speed of 60 km/h. It returns to the starting point at a speed of \( V \). If the average speed for the entire trip is 48 km/h, then what is the magnitude of \( V \)?

• A. 40 km/h
• B. 36 km/h
• C. 44 km/h
• D. 32 km/h

Hint:

Use harmonic mean formula for average speed over round trips with unequal speeds.

Answer 1

The Correct Option is A

Average speed for round trip is given by: \[ \text{Average speed} = \frac{2 \cdot u \cdot v}{u + v} \] Given: \( u = 60 \), average speed = 48. Solve: \[ 48 = \frac{2 \cdot 60 \cdot V}{60 + V} \Rightarrow 48(60 + V) = 120V \] \[ 2880 + 48V = 120V \Rightarrow 2880 = 72V \Rightarrow V = 40 \]