A train starts from Point A for point B and takes 2 hrs , another train starts from point B for point A and takes 3 hrs. After how much time will they cross each other?

Asked by  | 5th May, 2011, 12:00: AM

Expert Answer:

Let the distance between these two points be D, speed of 1st train (who covers the distance in 2 hours) be S1 and speed of 2nd train (who covers the distance in 3 hours) be S2.
We know that distance travelled = speed * time taken ......... (1)
For 1st train. D=S1*2, ==> S1=D/2
For 2nd train. D=S2*3, ==> S2=D/3
Let the two train meet at a distance of X in time T.
Total distance travelled by train when they will meet will be equal to D ....... (2)
==> S1*T + S2*T = D
==> (S1+S2)*T=D
==> (D/2 + D/3)*T=D
==> 5*D*T/6=D
==> T=6/5 = 1.2 hours

Answered by  | 24th May, 2011, 11:04: AM

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