arithmetic - two trains of equal length 120 metres move in the same direction the faster train completely overtakes the slower one in 15 seconds if the slower train were to move at half its speed the over taking would take in 10 seconds at what speed - skillgun

The total distance covered for over taking = length of the two trains = 120 +120 = 240
Speed of faster train be x m/s and slower train be y m/s
In the first case Relative speed = x-y
Relative Speed = Distance / Time taken = x-y = 240/15 = 16 m/s………(1)
In the second case, the slower train moves at half its speed
Relative Speed = x-0.5y = 240/10 = 24 m/s …………………..(2)
Solving equation 1 & 2 we get x = 32 and y = 16 .
The speed of the faster and slower trains are 32 m/s and 16 m/s respectively