Math Is Fun Forum

Monox D. I-Fly

Member

From: Indonesia

Registered: 2015-12-02

Posts: 2,000

[ASK] About Debit

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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Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away.
May his adventurous soul rest in peace at heaven.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: [ASK] About Debit

Hi;

What does fulfill mean here?

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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.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,640

Re: [ASK] About Debit

bobbym:  I think he means 'fill'.

Monox D. I-Fly:  I would do this as follows:

Let channel I fill at a rate of A units per minute; channel II at B units per minute; and channel III empty at C units per minute.  Let the tub contain V uniits.

Then we have

(A+B-C) x 80 = V and two more similar equations for you to work out.  Use these to find A, B and C in terms of V.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: [ASK] About Debit

Okay, thanks Bob.

Hi Monox D. I-Fly;

Bob's formulation of the problem will pop up if you just would set the problem up as a specific example. The set of equations is underdetermined, meaning it has fewer equations than unknowns. You will not get a unique answer but rather a set of possible solutions.

---

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.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,640

Re: [ASK] About Debit

hi bobbym,

I think it is ok.  There are four unknowns, A, B, C, and V but you can get A in terms of V and so on. 

The duration of each channel I and channel II fulfill the tub ....

  ie.  How long will it take to fill the tub using A on its own.  So the time will drop out without any 'V' in the answer.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

thickhead

Member

Registered: 2016-04-16

Posts: 1,086

Re: [ASK] About Debit

fulfill the tub= fill the tub full ; However that is Indian English.

Last edited by thickhead (2017-03-10 23:42:09)

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{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: [ASK] About Debit

Hmmm, I thought Monox D. I-Fly hailed from Indonesia...

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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.

Monox D. I-Fly

Member

From: Indonesia

Registered: 2015-12-02

Posts: 2,000

Re: [ASK] About Debit

Thanks everyone. Thickhead was right, that was what I meant. Indonesian words are mostly derived from India, anyway.

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Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away.
May his adventurous soul rest in peace at heaven.