Question

Two cities A and B are 360 km apart. A car goes from A to B with a speed of 40 km/h and returns to A with a speed of 60 km/h. What is the average speed of the car?

• A. 45 km/hr
• B. 50 km/hr
• C. 48 km/hr
• D. 55 km/hr

Hint:

For average speed of equal distances at different speeds, use harmonic mean formula.

Answer 1

The Correct Option is C

Step 1: Understand average speed for round trip
Average speed for two equal distances with different speeds is given by:
\[ \text{Average speed} = \frac{2 \times \text{speed}_1 \times \text{speed}_2}{\text{speed}_1 + \text{speed}_2} \] Step 2: Substitute values
\[ = \frac{2 \times 40 \times 60}{40 + 60} = \frac{4800}{100} = 48 \text{ km/hr} \] Thus, Option (C) 48 km/hr is correct.