How fast was the stream flowing?

Question

A girl is swimming downstream. In still water she can swim at 2km/h and the river is flowing with her. She covered a distance of 12km in 2h 24min. How fast was the stream flowing?

 

a. 5km/h                   b. 4km/h                   c. 3km/h                 d. 2km/h

Answer 1

First we have to make all units compayible, it is to have apples to apples.

2 Km/h = 2/60 km/min = 0.03 km/min

2h 24 min=144 min.

12km/144 min= 0.083 km/min

The stream speed will be 0.083-0.03 = 0.053 km/min

The stream speed is 0.053 * 60 = 3.18 km/hr.

 I would say answer c.