Sajjad1994
Train X and Train Y, traveling at their respective constant rates, are moving in the same direction along parallel tracks. Initially, Train X is behind Train Y by 18 kilometers, but after 4 hours, Train X is 6 kilometers ahead of Train Y.
Using the information given, identify an answer that could be the speed of Train X and an answer that could be the speed of Train Y, both in kilometers per hour (k/h). Make only two selections, one in each column.
Key Formula ----> Distance = Speed * Time
Train X : Let Speed = Sx , Time = Tx , Distance = Dx ; Dx = Sx * Tx
Train Y :
Let Speed = Sy , Time = Ty , Distance = Dy ; Dy = Sy * Ty
Now translate the lines one by one.
Initially, Train X is behind Train Y by 18 kilometers :So, Dx = Dy - 18. ....(eqn. 1)
but after 4 hours, Train X is 6 kilometers ahead of Train Y : After 4 hours means :
Time will be added by 4 [Sx * (Tx + 4)] = [Sy * (Ty + 4)] + 6
[Sx * Tx] + 4Sx = [Sy * Ty] + 4Sy + 6
4Sx - 4Sy - 6 = [Sy * Ty] - [Sx * Tx]
4Sx - 4Sy - 6 = 18 (From equation 1)
4Sx - 4Sy = 24 (Divide this complete euation by 4)
Sx - Sy = 6
From answer choices :
Sx = 54 and
Sy = 48Satisfies it.
Hope it helps.