The speed at which a person comes back home from his office is one-fourth of the speed at which he goes to his office. If the average speed during the entire round trip is 15 km/h, what was his speed while going to the office?

If a person travels a distance of 90 km at a speed of 45 km/h and another distance of 150 km at a speed of 50 km/h, what is his average speed for the entire journey?

Anita travels from place A to place B at a speed of 30 km/h, from place B to place C at 40 km/h, and from place C to place D at 120 km/h. If the distances between these places are equal, what is Anita's average speed (in km/h) during the entire journey?