Question

A boat goes 30 km/hr along the stream and 10 km/hr against the stream. The speed of the boat in still water (in km/hr) is​

Answer 1

Answer:

20 km/hr

Step-by-step explanation:

If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then: Speed downstream = (u + v) km/hr. Speed upstream = (u - v) km/hr. Hence,

u + v = 30km/hr

So, u = (30 - v) km/hr

u-v - 10 km/hr

Substituting u,

(30 - v) - v = 10km/hr

30 - 2v = 10km/hr

v = 10 km/hr

u = 20 km/hr

Hence, the speed of the boat in still water is 20 km/hr.