The speed of a motorbike in still water is 20 km/h.  It travels 300 km downstream and then return to the starting point.  If round trip takes a total of 40 hours, what is the speed of flow of river?

10

Solve by choosing option as by solving Quadratic Equation

T =  \(\frac{D}{S}\)

40 =  \(\frac{300}{20 + x}\) + \(\frac{300}{20 - x}\)

40 =  \(\frac{300 (20 - x) + 300 (20 + x)}{400 - x^2}\)

= 40 × (400 - x²)

= 6000 - 300x + 6000 + 300x

x = 10