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# M11-11

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Math Expert
Joined: 02 Sep 2009
Posts: 44586

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16 Sep 2014, 00:44
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Difficulty:

35% (medium)

Question Stats:

78% (01:25) correct 22% (01:55) wrong based on 86 sessions

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Tub A and tub B contain 540 liters of water each. Every minute tub A loses 25 liters of water while tub B loses 15 liters. If in $$X$$ minutes tub B will contain 6 times as much water as tub A, what is $$X$$?

A. 15
B. 20
C. 25
D. 30
E. 40
[Reveal] Spoiler: OA

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Math Expert
Joined: 02 Sep 2009
Posts: 44586

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16 Sep 2014, 00:44
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Official Solution:

Tub A and tub B contain 540 liters of water each. Every minute tub A loses 25 liters of water while tub B loses 15 liters. If in $$X$$ minutes tub B will contain 6 times as much water as tub A, what is $$X$$?

A. 15
B. 20
C. 25
D. 30
E. 40

The equation is $$6(540 - 25X) = 540 - 15X$$ from where $$X = 20$$.

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Intern
Joined: 10 Jul 2014
Posts: 42
Concentration: Technology, Strategy

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30 Jan 2015, 13:54
Bunuel wrote:
Official Solution:

Tub A and tub B contain 540 liters of water each. Every minute tub A loses 25 liters of water while tub B loses 15 liters. If in $$X$$ minutes tub B will contain 6 times as much water as tub A, what is $$X$$?

A. 15
B. 20
C. 25
D. 30
E. 40

The equation is $$6(540 - 25X) = 540 - 15X$$ from where $$X = 20$$.

Hi,
I find it hard to visualize this problem. I am following MGMAT approach of creating the table. Can you please explain a bit more for this problem?
Math Expert
Joined: 02 Sep 2009
Posts: 44586

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31 Jan 2015, 06:10
1
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Expert's post
pairakesh10 wrote:
Bunuel wrote:
Official Solution:

Tub A and tub B contain 540 liters of water each. Every minute tub A loses 25 liters of water while tub B loses 15 liters. If in $$X$$ minutes tub B will contain 6 times as much water as tub A, what is $$X$$?

A. 15
B. 20
C. 25
D. 30
E. 40

The equation is $$6(540 - 25X) = 540 - 15X$$ from where $$X = 20$$.

Hi,
I find it hard to visualize this problem. I am following MGMAT approach of creating the table. Can you please explain a bit more for this problem?

Every minute tub A, containing 540 liters of water, loses 25 liters of water, thus after x minutes it'll contain 540 - 25x liters of water.

Every minute tub B, containing 540 liters of water, loses 15 liters of water, thus after x minutes it'll contain 540 - 15x liters of water.

We are told that after x minutes tub B will contain 6 times as much water as tub A, thus 6(540 - 25x) = 540 - 15x.

Hope it's clear.
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Joined: 14 Mar 2016
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12 Sep 2017, 16:01
Thanks Bunuel! Excellent question. I'd like to further refine my solving on these types of problems - could you suggest some other examples/problems that will help me?
Math Expert
Joined: 02 Sep 2009
Posts: 44586

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12 Sep 2017, 21:03
vpustovoyt wrote:
Thanks Bunuel! Excellent question. I'd like to further refine my solving on these types of problems - could you suggest some other examples/problems that will help me?

17. Work/Rate Problems

For more check:
ALL YOU NEED FOR QUANT ! ! !

Hope it helps.
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Intern
Joined: 13 Oct 2017
Posts: 40

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12 Mar 2018, 02:45
Hi Bunuel,

How can I deploy the table method to answer this question?

I tried and failed to use it.

Rate * Time = Work
A: 25litres/min (under rate column) 540 litres (under work column)
B: 15 litres/min (under rate column) 540 litres (under work column)
B: X (under time column) 6A (under work column)

Can you please show me how you can answer the question using this method?

I ask because it's best to be consistent with a particular approach to most questions...and I can't for the life of me understand how you know how the X is inserted...when I tried your method I didn't know where to put the X so I did 540-15L = 6(540) - 25(6)L

Why for instance is it 25X and 15X respectively as opposed to 25/X and 15/x respectively? Especially since it's per minute - meaning divided by minutes.

Thanks.

Tosin
M11-11   [#permalink] 12 Mar 2018, 02:45
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# M11-11

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