Management Aptitude Test 2018 Paper

(b) Let the downstream and upstream speed be d km/h and u km/h, respectively.
Then, as per question,
$\frac{48}{\mathit{d}}+\frac{48}{\mathit{u}}$ = 14 ................(i)
Also, $\frac{4}{\mathit{d}}=\frac{3}{\mathit{u}}$ .............(ii)
Put the value of u from eq. (ii) in eq. (i)
⇒ $\frac{48}{\mathit{d}}+\frac{48}{\frac{3\mathit{d}}{4}}$ = 14
⇒ $\frac{48}{\mathit{d}}+\frac{48\times 3}{3\mathit{d}}$ = 14
⇒ $\frac{48\times 12}{3\mathit{d}}$ = 14 ⇒ d = 12 km/h
∴ u = $\frac{3\mathit{d}}{4}$ = $\frac{3\times 12}{4}$ = 9 km/h
Hence, rate of stream = $\frac{12-9}{2}=\frac{3}{2}$ = 1.5 km/h