Question

A motor boat whose speed is 9 km/hr in still water, goes 15 km downstream and comes back in a total time of 3 hours 45 minutes. Find the speed of the stream

Answer 1

Answer:

Step-by-step explanation:

Let the speed of stream be x .

15/(9+x) + 15/(9-x) = 3.75  

4/(9+x) + 4/(9-x) = 1

4(9-x) + 4(9+x)  = 81 - x²

36 - 4x + 36 +4x = 81-x²

72 = 81 - x²

x² = 9

x = ± 3

Speed of stream = 3 because speed cannot be negative.