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?
Answer & explanation
Correct answer: option 1
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