A man can row up stream at 4 km/h and downstream at 7 km/h. What is the rate of the current?
Answer & explanation
Correct answer: option 1
Let,
Speed of boat in still water= x
Speed of stream/current = y
According to the question:
Upstream speed (Us) = 4 km/hr i.e. x - y = 4km/hr -----1st equation
Downstream speed (Ds) = 7km/hr i.e. x + y = 7km/hr -----2nd equation
Subtracting 1st eq from 2nd we get
x + y - ( x- y) = 7 - 4
x + y - x + y = 3
2y = 3
y = \(\frac{ 3}{ 2}\) = 1.5 km/hr