Time and Distance Practice Test 2 with solutions

Let the speed of the slower car = x km/hour
The speed of the faster car = (x + 20) km/hour
$\frac{150}{\mathit{x}}-\frac{150}{\mathit{x}+20}$ = 2
⇒ $\frac{\mathit{x}+20-\mathit{x}}{{\mathit{x}}^2+20\mathit{x}}$ = $\frac{1}{75}$
${\mathit{x}}^2$ + 20x - 1,500 = 0
(x + 50) (x - 30) = 0
x = 30
So, the speed of the faster car = 50 km/hour
Time taken by the faster car = $\frac{150}{50}$ = 3 hours