Question

a train covers a certain distance in 15 hours how long it will take at twice the speed. Solve it how you did it

Answer 1

very simple 15 hours /2 speed =7.5 houres(7houres 30 minutes)

Answer 2

speed is inversely proportional to time
if speed is doubled then time is halved
so new time is 15/2=7.5 hrs