Question 448309
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Tutor @ikleyn has provided a response showing a solution by the method that is usually taught.<br>
Here is a solution using an alternative method.<br>
Consider the least common multiple of the three given times, which is 24 hours.<br>
In 24 hours...
pipe A could fill the tank 24/6 = 4 times;
pipe B could fill the tank 24/8 = 3 times; and
pipe C could fill the tank 24/12 = 2 times<br>
So in 24 hours the three pipes could fill the tank 4+3+2 = 9 times.<br>
That means the number of hours required for the three pipes together to fill the tank one time is 24/9 = 8/3.<br>
ANSWER: 8/3 hours, or 2 2/3 hours<r>