Question

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

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

Hint:

When same distance is traveled at two different speeds, use \( \frac{2ab}{a+b} \) to find the average speed.

Answer 1

The Correct Option is B

Step 1: Use average speed formula for round trip with equal distances \[ \text{Average speed} = \frac{2ab}{a + b} \] where \( a = 40 \, \text{km/hr},\quad b = 60 \, \text{km/hr} \) Step 2: Substitute values \[ \text{Average speed} = \frac{2 \times 40 \times 60}{40 + 60} = \frac{4800}{100} = \boxed{48 \, \text{km/hr}} \]