Math Is Fun Forum

Denominator

Member

Registered: 2009-11-23

Posts: 220

2 Taps and a Bath

Hi again,

I saw this question somewhere, but I forget, and I have no idea what to do to solve it:

Tap A takes X minutes to fill a bath, Tap B takes Y minutes to fill the same bath. How long would it take to fill the bath with both taps on (in terms of X and Y)?
I don't care about the answer but just how you figure it out.

It seems like a simple problem but I can't do it:\
Thanks

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bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: 2 Taps and a Bath

Hi;

It is not simple, everybody has to be shown this the first time.

That is the math. I think of it in terms of say 1 minute or 1 hour, whatever the units of the problem are.

If it takes A 5 minutes to fill a tub then it fills 1/ 5 of a tub in 1 minute. Tap B takes 10 minutes to fill it so it fills 1 / 10 of the tub per minute. Together they fill

So every minute they are filling 3 / 10 of the tub. So in 10 / 3 minutes they will fill it.

It should be clear for you to generalize this to any amount of taps. Or a couple of guys painting a house.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Denominator

Member

Registered: 2009-11-23

Posts: 220

Re: 2 Taps and a Bath

Oh yes,
thank you very much
I will remember this <3

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bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: 2 Taps and a Bath

Hi Denominator;

If you do remember it you will be doing better than I. I had to be told 5 times at least.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: 2 Taps and a Bath

Resistors in parallel also:

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman