Trains Boats and Streams Practice Test 2 with solutions

Let x km/hr and y km/hr be the speed of boat in still water and speed of current respectively; then
$\frac{20}{\mathit{x}+\mathit{y}}+\frac{6}{\mathit{x}-\mathit{y}}$ = 3 ... (i)
and also, $\frac{30]}{\mathit{x}+\mathit{y}}+\frac{12}{\mathit{x}-\mathit{y}}$ = 5
⇒ $\frac{15}{\mathit{x}+\mathit{y}}+\frac{6}{\mathit{x}-\mathit{y}}$ = $\frac{5}{2}$ ... (ii)
Solving equations (i) & (ii) we get, x + y = 10 and x – y = 6
Since, x = $\frac{1}{2}$ (10 + 6) = 8 km/hr.