A man can row 12 km/h in still water. He finds that it takes him twice as long to row upstream as to row downstream. What is the speed of the stream?
বিকল্পসমূহ (নিজের উত্তর যাচাই করতে ক্লিক করুন):
সঠিক উত্তর
2 (4 km/h)
বিস্তারিত ব্যাখ্যা ও বিশ্লেষণ:
Solution:
Speed in still water = 12 km/h
Speed of the stream = x km/h
Let the distance travelled is = D km
Time taken upstream = 2 × (Time taken downstream)
D/(12-x) = 2 × {D/(12+x)}
⇒ 1/(12-x) = 2/(12+x)
⇒ 12 + x = 24 - 2x
⇒ 3x = 12
∴ x = 4
So, Speed of the stream = 4 km/h
