Trains Boats and Streams Practice Test 3 with solutions

Let x km/hr and y km/hr be the speed of boat in still water and speed of current respectively; then
$\frac{40}{\mathit{x}-\mathit{y}}+\frac{55}{\mathit{x}+\mathit{y}}$ = 13 and also, $\frac{30}{\mathit{x}-\mathit{y}}+\frac{44}{\mathit{x}+\mathit{y}}$ = 10 ... (i)
⇒ $\frac{8}{\mathit{x}-\mathit{y}}+\frac{11}{\mathit{x}+\mathit{y}}$ = $\frac{13}{5}$ ... (i)
⇒ $\frac{15}{\mathit{x}-\mathit{y}}+\frac{22}{\mathit{x}+\mathit{y}}$ = 5 ... (ii)
Solving these two equations, we get x + y = 11 and x – y = 5
Since, x = $\frac{1}{2}$ (11 + 5) = 8 km/hr. and y = 11 – 8 = 3 km/hr.