Two trains are travelling in opposite direction at 72 km/h and 90 km/h. They cross each in 16s. If the length of the slower trains is 320 m, then find the length of the faster train (in m).

Options

A. 380
B. 420
C. 400
D. 425

Answer

C

Explanation

Relative speed = (72 + 80) km/h = 162 km/h
`= 162 xx (5)/(18) = 45 " m/s"`
Time taken to cross each other
`=(" Time sum of the lengths of two trains ")/("Relative speed")`
`16 = (320 +T)/( 45) " " ("where 'T' be the length of the faster train")`
720 = 320 + T
`therefore T_(2) = 720-320 = 400m`
Hence, the correct option is (c).