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

1