Question

The length of a train is 140 m long and it's speed is 72 km/h.how long will It take to cross a pole and a platform 220 m long

Answer 1

18 seconds. As the distance to be covered is

$d = 220 + 140 = 360$

using formula

$\frac{d}{s \times t} = 1 \\ ......(1)$

where, d is distance and s is speed,
and coverting kmph to m/min

$\frac{1km}{1h} = \frac{1000m}{60min.}$

we will get,

$\frac{72km}{1h} = \frac{72000m}{60min} = \frac{1200m}{1min} = \frac{20m}{1s}\\ ......(2)$

using (2) in (1) we get,

$\frac{360}{20m/s \times t} = 1$

which gives, t = .3 min = 18 seconds .