1 Answers

Option 2 : 2:00 PM

Given:

Length of 1st train = 100 meter

Length of 2nd train = 200 meter

Speed of 1st train = 18 km/h

Speed of 2nd train = 36 km/h

Concept used:

1.) Relative speed is defined as the speed of a moving object with respect to another.

2.) When two objects are moving in the same direction, relative speed is calculated as their difference.

3.) m/s = (km/h) × (5/18)

Formula used:

Speed = Distance/time

Distance = Speed × time

Relative speed when moving in same direction = a – b

Calculations:

Train 1st reaches at point C on 12 AM

Time taken by 1st train to reach at C = 12 AM – 10 AM = 2 hours

Distance between A to C = 18 × 2 = 36 km = 36000 meter

Total distance which is covered by 2nd train to cross the train = 200 + 36000 + 100 = 36300 m

Relative speed of both the trains = a – b = 36 – 18 = 18 km/h = 18 × (5\18) = 5 m/s

Total time taken by 2nd train to cross the 1st train = Distance/speed = 36300/5 = 7260 second

Time taken in hours = 7260/3600 = 2.01 hours ≈ 2 hours

∴ Time to meet of both the friends = 12 AM + 2 hours = 2:00 PM

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