Ashi can swim in still water at the rate of 6km per hour. After swimming in a stream, she realized that she takes twice the time to go upstream as she takes to go downstream. What is speed of the current?
Answer & explanation
Correct answer: option 2
Let,
Speed of Ashi in still water i.e. x = 6km/hr
Speed of stream/current - y
Upstream speed i.e. x - y = 6 - y km/hr
Downstream speed i.e. x + y = 6 + y km/hr
According to the question:
T = \(\frac{ D}{6 + y }\) --------1st equation ( downstream time)
2T = \(\frac{ D}{6 - y }\) --------2nd equation ( upstream time)
It can be deduced from the above equations that:
\(\frac{ 2D}{6 + y }\) = \(\frac{ D}{6 - y }\)
\(\frac{ 2}{6 + y }\) = \(\frac{ 1}{6 - y }\)
12 - 2y = 6 + y
3y = 6
y = 2 km/hr