I went to Point B from point A at 3 km/h and returned to A from B at 6 km/h.
First of all, because we do not know the distance between A and B, it should be made by ourselves.
In order to be easily calculated, it is assumed 6km which is the Lowest Common Multiple of 3 and 6.
The time it took to go is at 6km / 3km/h = 2 hours, the time of return is 6km / 6km/h = 1 hour.
Since the sum of the round-trip distance is 12km, average speed is 12km / (1 hour + 2 hour) = 4km / h.
Answer
4 km/h
Solution
Average speed should be calculated by the formula of
(total of advanced distance) / (total of the taken time).
(total of advanced distance) / (total of the taken time).
First of all, because we do not know the distance between A and B, it should be made by ourselves.
In order to be easily calculated, it is assumed 6km which is the Lowest Common Multiple of 3 and 6.
The time it took to go is at 6km / 3km/h = 2 hours, the time of return is 6km / 6km/h = 1 hour.
Since the sum of the round-trip distance is 12km, average speed is 12km / (1 hour + 2 hour) = 4km / h.
