Question 1209198
it took a train 65 seconds from starting to cross an iron bridge of length 1440m to completely pass over the bridge. It also took the train 75 seconds from when it entered a 1680m tunnel to completely pass through the tunnel.
Find the length Letand speed of the train.

Let speed of train be x m  
Let length of train be y m

Length of bridge be 1440 s

distance to cover = (y+1440)

time =65 s
65 = (y+1440)/x

65x = y+1440
65x-1440 =y..................1

For the other bridge

75 = (y+1680)/x

75x = y+1680
y= 75x -1680.............2

Equate both equations

75x-1680 = 65x - 1440
Rearrange

75x-65x = 1680-1440

10x = 240 
x =24 m/s
Speed of train = 24m/s

Plug value of x in 65x-1440 =y

65*24 -1440 = y 
y=120 m 

Length of train is 120 m