The speed of train A is equal to the speed of train B and the length of train A is 60 m more than that of train B. If train A crosses a pole in 15 seconds and train B crosses a pole in 12 seconds, then find the sum of the speed of trains A and B together?
A. 50 m/sec
B. 20 m/sec
C. 40 m/sec
D. 30 m/sec
E. None of these
Sol:
Let the speed of train A = x
And the speed of train B = x
The length of train B = y
And the length of train A = y+60
y + 60 = 15 * x—(1)
y = 12 * x —(2)
From (1) and (2),
12x + 60 = 15x
3x = 60
x = 20
y + 60 = 15 * 20
y = 300 – 60
y = 240
The speed of train A = 20 m/sec
And the speed of train B = 20 m/sec
The sum of the speed of trains A and B together
= 20 + 20 = 40 m/sec
