If a boat goes 7 km upstream in 42 minutes and the speed of the stream is 3 km/hr, then the speed of the boat in still water is

13 Km/hr

Speed  = \(\frac{Distance }{ Time}\)

Upstream speed i.e. x - y = \(\frac{7 }{42/60 }\) = 10 km/hr

Speed of stream i.e. y = 3 km/hr

Speed of boat in still water i.e. x = ?

x - y = 10, we know y = 3, so, x = 13 km/hr