A) 72 km/h |
B) 68 km/h |
C) 65 km/h |
D) 60 km/h |
A) 72 km/h |
Let length of the train = L
According to the question,
\( \Large \frac{L+300}{21} = \frac{L+240}{18} \)
=> \( \Large \frac{L+30}{7} = \frac{L+240}{6} \)
=> 6L + 1800 = 7L + 1680
Therefore, L = 120 m
Taking the length of the 2nd bridge into consideration,
Speed of train = \( \Large \frac{L+240}{18} = \frac{120+240}{18} m/s \)
= \( \Large \frac{360}{18} \times \frac{18}{5} km/h \)
= 72 km/h