A train covers a distance of 10 km in 12 minutes. If its speed is decreased by 5 km/hr, the time taken by it to cover the same distance is equal to :

September 1, 2016 September 1, 2016

A train covers a distance of 10 km in 12 minutes. If its speed is decreased by 5 km/hr, the time taken by it to cover the same distance is equal to :
[A] $20\ minutes$
[B] $15\ minutes$
[C] $\frac{40}{3}\ minutes$
[D] $40\ minutes$

$\mathbf{\frac{40}{3}\ minutes}$
Time = 12 minutes $= \frac{12}{60}\ hours = \frac{1}{5}\ hours$
Speed of train =
$= \frac{10}{\frac{1}{5}} = 50\ km/hr$
New speed = 50 – 5 = 45 km/hr
$\therefore Required\ Time = \frac{Distance}{Speed}$
$= \frac{10}{45} = \frac{2}{9}\ hour$
$= \frac{2}{9}\times 60 = = \frac{40}{3}\ minutes$
Hence option [C] is correct answer.