A man can row 90 km downstream and return in a total of 8 hours. If the speed of the boat in still water is four times the speed of the current, then the speed of the current is?
Answer & explanation
Correct answer: option 4
Ratio of speed of boat and current = 4 : 1
ATQ, \(\frac{90}{4R + 1R}\) + \(\frac{90}{4R - 1R}\) = 8
\(\frac{18}{R}\) + \(\frac{30}{R}\) = 8
\(\frac{48}{8}\) = R
R = 6
Speed of current = 1R = 1 × 6 = 6 km/hr