Trains Boats and Streams Practice Test 4 with solutions

Let the original speed of Delhi Express = x km/hour
Time taken to cover 2,000 km = $\frac{2000}{\mathit{x}}$
New speed = x + 50
New time = $\frac{2000}{\mathit{x}+50}$
According to the question,
$\frac{2000}{\mathit{x}+50}$ = $\frac{2000}{\mathit{x}}-2$
$\frac{2000}{\mathit{x}+50}$ = $\frac{2000-2\mathit{x}}{\mathit{x}}$
2,000x = 2,000x + 1,00,000 - $2{\mathit{x}}^2$ - 100x
$2{\mathit{x}}^2$ + 100x + 1,00,000 = 0
${\mathit{x}}^2$ + 50x + 50,000 = 0
${\mathit{x}}^2$ + 250x - 200x + 50,000 = 0
(x + 250) (x - 200) = 0
x = 200 km/hour