A motor boat whose speed is 18 km/hr in still water takes 1hr more to go 24 km

Quadratic Equations (10)

A motor boat whose speed is 18 km/hr in still water takes 1hr more to go 24 km upstream than to return downstream to the same spot. Find the speed of the stream.

Answer

Let the speed of stream be x km/hr. 

The speed of the boat upstream = (18 - x) km/hr 

Speed of the boat downstream = (18 + x) km/hr 

As given in the question, 

$ \frac{24}{18 -x} - \frac{24}{18 + x} = 1 $

x2 + 48x - 324 = 0

(x + 54)(x - 6) = 0 

$x \ne -54, .. x = 6 $

Speed of the stream = 6 km/hr.

Exam Year: 2018