Question

Naresh Kumar drives his car to his office with the speed of 40 km per hour and returns along the same route with the speed of 60 km per hour. His average speed for the entire round trip is

• A. 50 km per hour
• B. 48 km per hour
• C. 45 km per hour
• D. None of these

Answer 1

Answer: (B)

Distance travelled by car is $x+x=2\times x$.

Time taken by car to go to office is $\frac{x}{40}$.

Time taken by car for return journey is $\frac{x}{60}$.

Total time taken is equal to $\frac{x}{40}+\frac{x}{60}=\frac{x}{24}$.

Average speed is equal to total distance travelled by car divided by total time taken.

so, average speed is equal to $\frac{2\times x}{\frac{x}{24}}=48$ km per hour.