A person travels a certain distance at a speed of 18 km/h and returns to the starting point at 12 km/h. If he takes 2 hours 55 minutes for the whole journey, the distance of one way is:

Let's assume the distance of one way is 'd' km.

A person travels a certain distance at a speed of 18 km/h and returns to the starting point at 12 km/h. If he takes 2 hours 55 minutes for the whole journey.

$$\frac{d}{18}+\frac{d}{12}\ =\ 2\frac{55}{60}$$

$$\frac{d}{18}+\frac{d}{12}\ =\ 2\frac{11}{12}$$

$$\frac{d}{18}+\frac{d}{12}\ =\ \frac{35}{12}$$
$$\frac{d}{3}+\frac{d}{2}\ =\ \frac{35}{2}$$
$$\frac{2d}{6}+\frac{3d}{6}\ =\ \frac{35}{2}$$
$$\frac{5d}{6}\ =\ \frac{35}{2}$$
$$\frac{d}{3}\ =\ 7$$

distance of one way = d = 21 km