(A) 56 Meter
(B) 120 Meter
(C) 179 Meter
(D) 200 Meter
Correct Option is: D
Let the length of the goods train be x km and its speed be y km/hr.
Then, speed relative to first boy = (y-4) km/hr.
Speed relative to second boy = (y-8) km/hr.
x/y-4 = 18/60*60 and x/y-8 = 20/60*60
3600x =18y -72 ………….(1)
3600x = 20y – 160……….. (2)
From (1) and (2),
20y- 160 = 18y -72
2y = 88
y =44………………….(3)
substitute y value in (1) ,
x= (18*44)- 72 / 3600
= 720/3600
= 0.2*1000
= 200 m
Therefore the length of the goods train is 200 m