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  • 1 Post By Monox D. I-Fly
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March 10th, 2017, 10:35 PM   #1
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A water tub has 3 water channels. Channel I and II for filling the tub and channel III to empty it. Those 3 channels together fulfill the tub for 1 hour and 20 minutes. Channel I and II together fulfill the tub for 1 hour and 12 minutes from the empty condition. Channel II and III together fulfill the tub for 4 hours from the empty condition. The duration of each channel I and channel II fulfill the tub and channel III empties the tub are...

Well, I don't know where to start. But if channel I and II together (without channel III being open) fulfill the tub in 1 hour and 12 minutes, does it mean that channel III can empty the tub just within 8 minutes (because 01.20 - 01.12)?
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March 10th, 2017, 10:45 PM   #2
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I would begin by defining $C_1,\,C_2,\,C_3$ as the flow rates of the 3 channels, in tubs per minute.

From the given information, we know:

$\displaystyle C_1+C_2-C_3=\frac{1}{80}\tag{1}$

$\displaystyle C_1+C_2=\frac{1}{72}\tag{2}$

$\displaystyle C_2-C_3=\frac{1}{240}\tag{3}$

Suppose you subtract (3) from (1)...what do you get?
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March 10th, 2017, 10:56 PM   #3
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$\displaystyle C_1=\frac{1}{120}$
$\displaystyle C_2=\frac{1}{180}$
$\displaystyle C_3=\frac{1}{720}$
Am I right?
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March 10th, 2017, 10:58 PM   #4
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Quote:
Originally Posted by Monox D. I-Fly View Post
$\displaystyle C_1=\frac{1}{120}$
$\displaystyle C_2=\frac{1}{180}$
$\displaystyle C_3=\frac{1}{720}$
Am I right?
Yes, those are the same values I obtained.
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