A train x running at 74 km/h crosses another train y running at 52 km/h in the opposite direction in 12 seconds. If the length of y is two-thirds that of x, then what is the length of y (in m)?

168

Relative speed = ( 74 + 52 ) = 126 km/h

126 km/h = 126 × \(\frac{5}{18}\) m/sec = 35 m/sec

Time taken = 12 sec

Distance = Speed × Time

Distance = 35 × 12 = 420 km

According to question ,

Ratio of length of       x    :   y

                               3     :   2

5R = 420 km

1R = 84 km

Length of train y = 2R = 2 × 84 = 168 km

So , length of train y is 168 km.