Train A, 220m long, can cross a platform 340 m long in 32 sec. If the respective ratio of speed of trains A and B is 7 : 9 and the length of train B is 270 m, how much time (in sec) would train B take to cross an electric pole ?
Train A, 220m long, can cross a platform 340 m long in 32 sec. If the respective ratio of speed of trains A and B is 7 : 9 and the length of train B is 270 m, how much time (in sec) would train B take to cross an electric pole ?
1). 18
2). 12
3). 20
4). 22
2 answers
Length of train A = 220 m
=> Speed of train A = $\frac{220 + 340}{32}$
= $\frac{560}{32} = 17.5$ m/s
Speed of train A : Speed of train B = 7 : 9
=> Speed of train B = $\frac{9}{7} \times 17.5$
= $9 \times 2.5 = 22.5$ m/s
Length of train B = 270 m
$\therefore$ Time taken by train B to cross the pole = $\frac{270}{22.5}$
= 12 sec
Length of train A = 220 m
=> Speed of train A = $\frac{220 + 340}{32}$
= $\frac{560}{32} = 17.5$ m/s
Speed of train A : Speed of train B = 7 : 9
=> Speed of train B = $\frac{9}{7} \times 17.5$
= $9 \times 2.5 = 22.5$ m/s
Length of train B = 270 m
$\therefore$ Time taken by train B to cross the pole = $\frac{270}{22.5}$
= 12 sec