Pipe A alone can fill a tank in 8 minutes. Pipe B alone can fill the same tank in 12 minutes. Both the pipes are opened together when the tank is empty. However, Pipe B is closed 3 minutes before the tank is full. In what time did the tank get filled?

A) 6 minutes
B) 8 minutes

C) 10 minutes
D) 12 minutes

Correct answer:
A) 6 minutes

Description for Correct answer:
A Pipe A is kept open till the tank gets filled.

Let the time for which Pipe A is kept open = t minutes

Therefore, pipe B was kept open for (t - 3) minutes only.

Pipe A fills \( \Large \frac{1}{8} \)th of the tank in a minute and pipe B fills \( \Large \frac{1}{12} \)th of the tank every minute.

Together (A was open for t minutes and B for t-3 minutes) pipe A and pipe B fill ONE full tank

i.e. \( \Large \frac{t}{8}+\frac{t-3}{12}=1\ or\ \frac{3t+2t-6}{24}\ or\ 5t = 30\ or\ 5=6 minutes \)

Please provide the error details in above question

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