Question

A train running at 25 km/hr takes 18 seconds to pass a platform. Further, it takes 12 seconds to pass a man walking at 5 km/ hr in the opposite direction. Find the sum of the length of the train and that of the platform.

Answer 1

Step-by-step explanation:

Given  

A train running at 25 km/hr takes 18 seconds to pass a platform. Further, it takes 12 seconds to pass a man walking at 5 km/ hr in the opposite   direction. Find the sum of the length of the train and that of the platform.

 We know that Distance = speed x time

We need to convert km/hr to m/hr

So we get 25 x 1000 = 25000 m/hr.

So time = 18 secs = 18 x 1/60 x 60

                            = 18 / 3600

Now distance = 25000 x 18 / 3600

                      = 125 m

OR  

 Speed of train = 25 + 5 = 30 km/hr

                                         = 30 x 5/18 = 25 / 3 m/s

Distance travelled in 12 secs will be  

                                       = 25 / 3 x 12 = 100 m

Speed of the train = 25 km / hr = 25 x 5/18 = 125 / 18 m/sec

Distance travelled in 18 secs at this speed = 125 / 18 x 18 = 125 m

Therefore length of train + length of platform = 125 m

Now length of platform will be 125 – 100 = 25 m