You can put this solution on YOUR website! A train passes two bridges of lengths 800 m and 400 m in 100 seconds and 60 seconds respectively The length of the train is?
:
Let s = the speed of the train in meter/sec
Let L = length of the train
:
Write a distance equation for each bridge; dist = speed * time
Train + bridge = total dist
L + 800 = 100s
L + 400 = 60s
:
Multiply the 1st equation by 6, multiply the 2nd equation by 10
10L + 4000 = 600s
6L + 4800 = 600s
---------------------subtraction eliminates s, find L
4L - 800 = 0
4L = 800
L =
L = 200 meters is the length of the train
:
:
Check the solution by finding the speed, using the 1st equation
200 + 800 = 100s
1000 = 100s
s = 10 meter/sec is the speed
:
Check solution in the 2nd equation
200 + 400 = 60(10); confirms our solution of L = 200
