An aeroplane flies from place A to place B at the speed of 500 kms/hour. On the return journey, its speed is 700 kms per hour. The average speed of the aeroplane for the entire journey is

The correct answer is (b) 583 kms/hour.

The average speed is not just the average of 500 kms/hour and 700 kms/hour. This is because the aeroplane travels for a longer time on the journey at 500 kms/hour than it does at 700 kms/hour.

To calculate the average speed, we need to know the total distance travelled and the total time taken. The total distance travelled is 2 * 500 = 1000 km.

The total time taken is 500 / 500 + 700 / 700 = 12 hours.

The average speed is therefore 1000 / 12 = 583 kms/hour.