A boat moving upstream takes 6 hours 36 minutes to cover a certain distance while it takes 3 hours to cover the same distance downstream. What is the ratio of the speed of boat in still water to the speed of stream ?

8 : 3

The correct answer is option (4) : 8 : 3

Given, Time taken in upstream = 6.6 hours

Time taken in downstream = 3 hours

$\frac{x+y}{x-y}=\frac{6.6}{3}$

$3x+3y=6.6x-6.6y$

$9.6y= 3.6x$

$\frac{x}{y}=\frac{9.6}{3.6}=\frac{8}{3}$ i.e $8 : 3$