Question

A person travels from his house to his office by scooter at a speed of 40 km per hour. While returning, he travels at a speed of 20 km per hour. If the distance from his house to office is 5 km, what is his average speed of travelling both ways:

1. 30 km per hour
2. 25 km per hour
3. 26 * 2/3 km per hour
4. 30 * 1/3 km per hour