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Q.
A train $T$ travelling at a speed of $54 kmph$ passes an electric pole in 20 s. Find the time taken by it to cross a bridge of length $900 m$ (in seconds).
Time and Distance
Solution:
Let the length of the train be $L m$.
$\frac{L}{(54)\left(\frac{5}{18}\right)}=20 $
$(\because 1 km / h =\frac{5}{18} m / s ) \text { i.e., } L=300 $
$\text { Required time }=\frac{L+900}{(54)(\frac{5}{18})}=\frac{1200}{15} $
$=80 s $