A person travels from X to Y at a speed of 40 kmph and returns by increasing his speed by 50%. What is his average speed for both the trips?

To find the average speed for the entire journey, follow these steps:

1. Identify the speeds: The speed from X to Y is 40 kmph. The return speed is increased by 50 percent. 50 percent of 40 is 20, so the return speed is 40 plus 20, which equals 60 kmph.

2. Use the average speed formula: When the distance for both trips is the same, the average speed is calculated using the harmonic mean formula: 2 times speed one times speed two divided by the sum of the speeds.

3. Calculate the value: Average speed equals 2 times 40 times 60 divided by 40 plus 60. This equals 4800 divided by 100. The result is 48 kmph.

Therefore, option C is the correct answer.