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babi_gurl · May 19, 2007, 07:27 PM

Hey I need some help with this question;
A tank can be filled in 6 hrs using two pipes. The larger pipe alone would fill it 5 hrs sooner than the smaller pipe alone. How long would each pipe alone take?

galactus · May 20, 2007, 04:00 AM

Try setting it up like so:

$\underbrace{\frac{1}{t}}_{\text{large pipe}}+\overbrace{\frac{1}{t+5}}^{\text{small pipe}}=\frac{1}{6}$

Solve for t

babi_gurl · May 20, 2007, 04:21 AM

hey thxx but can u please explain how u came up with that equationnn

galactus · May 20, 2007, 04:36 AM

Anytime you see one of these 'pipe' problems it is convenient to introduce the part of the tank filled in 1 hour.

1/t = the part of the tank filled by the large pipe in 1 hour.

1/(t+5) is the part of the tank filled by the small pipe in 1 hour, because it takes 5 hours longer to fill than the large one.

1/6 is the part of the tank filled by both in 1 hour.

So, we have:

(part filled by large pipe in 1 hour)+(part filled by small pipe in 1 hour)=part filled by both in 1 hour.

See?

babi_gurl · May 20, 2007, 04:41 AM

Ohh I get it!! Lol thanks so much XD

galactus · May 20, 2007, 05:14 AM

You're so welcome. You're one of the few posters on this site who even bother to respond back, let alone say thanks.