Question

A train travels 360 km at a uniform spped. If the speed had been 5km/h more,it would have taklen 1 hour less for the same journey.Find the speed of the train.

Answer 1

Let speed be x km/h, as time = distance/speed

$\Rightarrow \frac{360}{x}-\frac{360}{x+5}=1\Rightarrow 360\left(\frac{5}{x(x+5)}\right)=1\Rightarrow 1800=x^2+5x$

$\Rightarrow x^2+5x-1800=0$

$\Rightarrow x=\frac{-5\pm \sqrt{25+7200}}{2}=\frac{-5\pm \sqrt{7225}}{2}=\frac{-5\pm 85}{2}=\frac{80}{2}=40$