Question

Annabelle is taking the train to see her boyfriend on Valentine's day! The train is 100 meters long and it takes 30 seconds to cross a 400m bridge. What speed is the train going at?

Answer 1

According to question,

length of train   L = 100 m
length of bridge   D = 400 m

Time taken    T = 30 sec
 

thus    speed of train   =  D - L / T
                                    =  400 - 100 / 30
                                    =  300 / 30
                                    = 10 m/sec

Answer 2

Given :

Length of the train=100m
t=30 sec
Bridge length =400m

Speed=Total distance/Time

Total distance=length of bridge +length of train
=400+100=500m

Speed=500/30
=50/3 m/s
1km/hr=5/18 m/s
Speed=50x18/15
=60km/hr
∴ Speed of train=60km/hr