Quant Boosters  Vikas Saini  Set 1

Let assume length of the train is ‘L’ and speed of train = a.
Speed of man 1 = b.
Speed of man 2 = c.
20 = L / a – b.
18 = L / a + c.
18a + 18c = 20a – 20b.
a = 10b + 9c.
Distance of two men = 600 x (a + c).
Time = 600(a+c) – 600(b+c) / (b+c)
= 600 ( a – b) / (b + c)
= 600 (10b + 10c – b) / (b + c)
= 5400 seconds
= 90 min (ans)