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 will be :
Answer: 13 minutes 20 sec
Notes: Speed of train $latex = \frac{Distance}{Time}&s=1$ $latex =\frac{10}{\frac{12}{60}}km/h&s=1$ $latex =\frac{10\times 60}{12} = 50km/h&s=1$ New Speed $latex = 45km/h&s=1$ ∴ Required Time $latex = \frac{10}{45}hour&s=1$ $latex = \frac{2}{9}\times 60 minutes&s=1$ $latex = \frac{40}{3} minutes&s=1$ $latex = 13 minutes 20 seconds$ Hence option [D] is correct answer.

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