Two boats are 50 km apart from each other in the direction of the flow of river. The speed of each boat in still water is 20 km/hr. They both start moving towards each other at same point of time. After how much time will they meet? (Assume that the river is straight and has no turns)
Solution
Correct Answer: Option B
Speed of each boat in still water = 20 km/hr
Suppose the speed of stream is v km/hr.
⇒ Speed of boat that goes upstream = (20 – v) km/hr
And, Speed of boat that goes downstream = (20+v) km/hr
Suppose the boats meet after T hours.
We know, Distance = Speed × Time
⇒Distance covered by boat moving upstream = (20-v) km/hr × T hr = (20-v)T km
⇒Distance covered by boat moving downstream = (20+v) km/hr × T hr = (20+v)T km
Now, total distance covered by boats should be equal to 50 km.
⇒ (20 – v)T + (20+v)T = 50
⇒ 40T = 50
⇒ T = 1.25 hours = 1 hour + (0.25 × 60 minutes) = 1 hour and 15 minutes
∴Time taken for the boats to meet = 1 hour and 15 minutes
Practice More Questions on Our App!
Download our app for free and access thousands of MCQ questions with detailed solutions