Question

A freight train left Delhi for Mumbai at an average speed of 40 km/hr. Two hours later, an express train left Delhi for Mumbai, following the freight train on a parallel track at an average speed of 60 km/hr. How far from Delhi would the express train meet the freight train? 

(a) 480 km 

(b) 260 km 

(c) 240 km 

(d) 120 km

Answer 1

Correct option (c) 240 km

Explanation:

Speed of freight train = 40 km/hr and Speed of express train = 60 km/hr 

Hence, relative velocity = 60 – 40 = 20 km/hr 

Distance travelled by freight train in 2 hours = Speed of freight train × 2 = 40 × 2 = 80 km 

So, time taken by express train to catch freight train = Distance/Relative speed = 80/20 = 4 hr 

Distance from Delhi at this moment = Speed of express train × 4 = 60 × 4 = 240 km