A motor boat can travel at 10 Km/hr in still water. It traveled 91 Km downstream in a river and then returned taking altogether 20 hrs. find the rate of flow of river in Km/hr?
Answer & explanation
Correct answer: option 1
Speed of boat in still water i.e. x = 10 km/hr
Speed of stream/current i.e. y = ?
Downstream speed = 10 + y
Upstream spead = 10 - y
According to the question:
\(\frac{ 91}{\text{10 + y} }\) + \(\frac{ 91}{\text{10 - y} }\) = 20
In these type of questions, where quadratic equations form it is always better to solve the questions by the options.
Put all the options and see which value of y from the options satisfy the above equation.
So, the answer is 3