Two pipes A and B would fill the tank in 20 and 30 minutes respectively. Both pipes being open, find when A must be turned off so that the tank may be just filled in 15 minutes.
বিকল্পসমূহ (নিজের উত্তর যাচাই করতে ক্লিক করুন):
সঠিক উত্তর
ক (After 10 mins)
বিস্তারিত ব্যাখ্যা ও বিশ্লেষণ:
Solution:
Let, after x minutes pipe A must be turned off.
Part fill by (A + B ) in 1 minutes = (1/20+ 1/30) = 1/12
Part fill by (A + B ) in x minutes = x/12
Then, pipe B does the job = (15 - x) minutes
In (15 - x) minutes Pipe B can fill the tank (15 - x) part
ATQ,
x/12 + (15 - x)/30 = 1
⇒ (5x + 30 - 2x)/60 = 1
⇒ 3x + 30 = 60
⇒ 3x = 30
⇒ x = 10
