Question

a train run a certain distance in 15 hours how long will it take at twice the speed​

Answer 1

Let the speed be 's' and distance be 'd'.

$time = \frac{distance}{speed }$

$So, \: 15 \: hours = \frac{d}{s}$

$New \: time, \: t' = \frac{d}{2s} \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \frac{1}{2} \times 15 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 7.5 \: hours$

Answer 2

Answer:

7.5 hours In fraction 15/2