A boat can travel 21 km in 3 hours going upstream. It can travel 55 km in 5 hours going downstream. What is the speed of the stream?
Answer & explanation
Correct answer: option 4
Let the speed of the boat and stream is x and y respectively.
A boat can travel 21 km in 3 hours going upstream.
= x - y = \(\frac{21}{3}\)
= x - y = 7 km/hr ...........(A)
It can travel 55 km in 5 hours going downstream.
= x + y = \(\frac{55}{5}\)
= x + y = 11km/hr.............(B)
Subtracting Equation (B) to equation(A)
= 2y = 4
Speed of the stream (y) = 2