Bihar Police Constable Model Paper 7

Given:
Boat goes 50 km along the distance in = 10 hrs
Speed of current = 2 km/hr
Formula:
Speed = distance/time
If speed of boat and stream be x and y km/hr respectively, then
Upstream speed = (x - y) km/hr
Downstream speed = (x + y) km/hr
Calculation:
Let speed of boat be x km/hr
Downstream speed = (x + 2) km/hr
According to the question
(x + 2) = 50/10
⇒ (x + 2) = 5
⇒ x = 5 – 2
⇒ x = 3
Speed of boat is 3 km/hr
Upstream speed = 3 – 2 = 1 km/hr
∴ Time taken by boat to cover 30 km upstream = 30/1 = 30 hrs