Concept of “Train"-05

Question: Two station A and B are 110 km apart on a straight line. A train starts from A at 8 a.m. and travels towards B at the rate of 40 km/hr. 2 hours later another train starts from B and travel towards A at the rate of 50 km/hr. When will the first train meet to the second train?      [Ans. (d) 10:20 A.M.]

(a) 11 am   (b) 9 am   (c) 10.15 am  (d) 10.20 am   (e) None of these

Solution: 

Detailed explanation:

Concept: 1. “Relative speed is used, when both the body move to start at the same time.”

                 2. “When the bodies are moving in the opposite directions, the relative speed is the sum of the speeds”

Two station A and B are 110 km apart on a straight line. A train starts from A at 8 a.m. and travels towards B at the rate of 40 km/hr. So, the distance described in 2 hrs is 40×2 = 80 km and the train reaches at C at 10 AM.

2 hours later another train starts from B and travel towards A at the rate of 50 km/hr.

Relative speed = (40 + 50) km/h = 90 km/h

Distance = (110 – 80) km = 30 km

Time taken by two trains to meet = 30 km/90 km/h = 1/3 hour = 20 minutes

Therefore, the first train meet to the second train at 10:20 AM Ans.