Question

Two trains start at the same time from points A and B towards each other and after crossing each
other, they take 25 hours and 9 hours in reaching points B and A, respectively. Find the ratio of speeds
of trains starting from A to that of starting from B.
(A) 53
(B) 3.5
(C) 4.5
(D) 5:4​

Answer 1

Given :- Two trains start at the same time from points A and B towards each other and after crossing each

other, they take 25 hours and 9 hours in reaching points B and A, respectively.

To Find :-

• Find the ratio of speeds of trains starting from A to that of starting from B.

Formula used :-

• S(1) : S(2) = √T(2) : √T(1)
• S(1) = Speed of First Train.
• S(2) = Speed of Second Train.
• T(1) = After Crossing Each other Time taken by first Train to Reach opposite Point.
• T(2) = After Crossing Each other Time taken by second Train to Reach opposite Point.

Solution :-

Given that, after crossing each other, they take 25 hours and 9 hours in reaching points B and A, respectively.

So,

• T(A) = 25 Hours. = After Crossing Each other Time taken by Train A to Reach Point B.
• T(B) = 9 Hours. = After Crossing Each other Time taken by Train B to Reach Point A.

Therefore,

→ S(A) : S(B) = √T(B) : √T(A)

→ S(A) : S(B) = √9 : √25

→ S(A) : S(B) = 3 : 5 (Ans.) (Option B).

Hence, The ratio of speeds of trains starting from A to that of starting from B is 3 : 5.