A boat covers 143 km upstream in 13 hours and the same distance downstream in 11 hours. What is the speed (in km/hr) of the boat in still (without stream) water?
বিকল্পসমূহ (নিজের উত্তর যাচাই করতে ক্লিক করুন):
সঠিক উত্তর
1 (12 km/hr)
বিস্তারিত ব্যাখ্যা ও বিশ্লেষণ:
Solution:
Let,
the speed (in km/hr) of the boat in still (without stream) water is x km/hr and speed of stream is y km/hr
Now
143/(x - y) = 13
⇒ 13 (x - y) = 143
⇒ x - y = 11..........(1)
143/(x + y) = 11
⇒ 11 (x + y) = 143
⇒ x + y = 13..........(2)
(1) + (2)
⇒ x - y + x + y = 13 + 11
⇒ 2x = 24
∴ x = 12 km/hr
