A, B and C are the three place on a river where B is equidistant from A and C. Monika can row from A to B and back in 9 hours and from A to C in 5 hours. Find the ratio of speed of his boat in still water with that of the current.
Answer & explanation
Correct answer: option 3
Let the distance AC be 2d
so AB = d
\(\frac{d}{x + y}\) + \(\frac{d}{x - y}\) = 9 ---(i)
\(\frac{2dx}{(x + y)(x -y)}\) = 9 ---(i)
\(\frac{2d}{x + y}\) = 5 ---(ii)
Divide (i) by (ii)
\(\frac{x}{x - y}\) = \(\frac{9}{5}\)
\(\frac{1}{1 - \frac{y}{x}}\) = \(\frac{9}{5}\)
\(\frac{y}{x}\) = \(\frac{4}{9}\)
or x : y = 9 : 4