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# A rabbit on a controlled diet is fed daily 300 grams of a

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Intern
Joined: 08 Sep 2006
Posts: 39
A rabbit on a controlled diet is fed daily 300 grams of a  [#permalink]

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Updated on: 06 Jun 2014, 01:39
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Question Stats:

81% (02:16) correct 19% (02:34) wrong based on 1741 sessions

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A rabbit on a controlled diet is fed daily 300 grams of a mixture of two foods, food X and food Y. Food X contains 10% protein and food Y contains 15% protein. If the rabbit's diet provides exactly 38 grams of protein daily, how many grams of food X are in the mixture.

A. 100
B. 140
C. 150
D. 160
E. 200

Originally posted by tinman1412 on 26 Jul 2007, 08:45.
Last edited by Bunuel on 06 Jun 2014, 01:39, edited 1 time in total.
Edited the question and added the OA.
Director
Joined: 26 Feb 2006
Posts: 609

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26 Jul 2007, 09:17
15
1
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tinman1412 wrote:
A rabbit on a controlled diet is fed daily 300 grams of a mixture of two foods, food X and food Y. Food X contains 10% protein and food Y contains 15% protein. If the rabbit's diet provides exactly 38 grams of protein daily, how many grams of food X are in the mixture.

a)100
b)140
c)150
d)160
e)200

The answer is B)140, but I do not understand the OG explanation. Can someone provide their approach to this question in detail

Thanks,

in fact one eq is enough: .1x + .15(300-x) = 38

solve for x, x = 140
##### General Discussion
Manager
Joined: 22 May 2007
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26 Jul 2007, 08:52
4
2
Set up two equations.

We know that 10%x+15%y=38 grams or .1x+.15y=38

We also know that x+y=300 grams.

2 eq. with 2 variables. Solve them and you should get it.
Intern
Joined: 26 Aug 2006
Posts: 18

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26 Jul 2007, 09:35
6
2
tinman1412 wrote:
A rabbit on a controlled diet is fed daily 300 grams of a mixture of two foods, food X and food Y. Food X contains 10% protein and food Y contains 15% protein. If the rabbit's diet provides exactly 38 grams of protein daily, how many grams of food X are in the mixture.

a)100
b)140
c)150
d)160
e)200

The answer is B)140, but I do not understand the OG explanation. Can someone provide their approach to this question in detail

Thanks,

Much simpler method is there...
38 gms means approx. 12.66%. Then use the mixture alligation formula to calculate the ratio of X to Y, ie,

X/Y= (15-12.66)/(12.66-10)=2.33/2.66.
Hence amt of X in total mixture is 300*2.33/(2.33+2.66)=139.2~140
Manager
Joined: 21 Jun 2006
Posts: 208

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26 Jul 2007, 10:16
D

Assume x grams is of mixture A and 300-x is of mixture B
Eqn is:

(300-x)*.1 + .15x = 38 (10% and 15% protein in Mixtures A and B respectively)

Solve for x =160
CEO
Joined: 07 Jul 2004
Posts: 2917
Location: Singapore

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27 Jul 2007, 01:20
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4
0.1x + 0.15y = 38

x+y = 300
x = 300-y

so 0.1(300-y) + 0.15y = 38
30-0.1y + 0.15y = 38
0.05y = 8
y = 160 grams

then x = 140 grams.

Ans B
Intern
Joined: 26 Aug 2006
Posts: 18

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27 Jul 2007, 04:35
tinman1412 wrote:
I was just wondering. I know there are many different ways to solve math problems, but is there a prefer method when solving Mixture Problems?

Its wat you feel comfortable with or the one which you do faster and accurately. You have to develop that approach by practice.
Atleast I think so. I solved the problem using Mixtures & Alligation formula coz I feel comfortable with that.

Sunil
Manager
Joined: 02 Jul 2007
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13 Aug 2009, 04:37
2
MGMAT has a great method that has really helped me to do these problems quickly.

For mixture problems, set up a chart:

the two different mixtures go on the right hand side, the quantities of each go on the top:

Protein Other
X

Y

The problem says the two mixtures are added together to produce a new mixture totaling 300 grams, so add to the chart:

Protein Other Total
X X

Y Y

X+Y 300

Now add the information about how much protein is in each mixture

Protein Other Total
X .1X X

Y .15Y Y

X+Y 38 300

Now there are two equations with 2 variables:

.1X + .15Y=38
X + Y = 300

Simple method, but it really helps break down harder questions.
Intern
Joined: 22 Jun 2010
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22 Jun 2010, 16:23
1
can someone explain the logic of the mixture and allegation formula?

the ratio of (difference between the high value and new percentage)
over
(diff b/t high and new) + (diff b/t new and low value)

what does this ratio represent and why, when multiplying the whole to it does it give you the amount in final.....
Intern
Joined: 20 Sep 2010
Posts: 2

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23 Sep 2010, 01:13
3
3
We know that
1.00x+1.00y=300

and that
0.10x+0.15y=38

so
0.10x+0.15y=38
*10=
1.00x+1.50y=380

Align them under eachother
1.00x+1.50y=380
1.00x+1.00y=300

Means 0.50y=80
80*2=160
y=160
x=300-y
x=300-160
x=140
Intern
Joined: 07 Sep 2010
Posts: 4

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24 Sep 2010, 02:21
let x= mixture A ,, then 300-x is Mixture B

.0.1 x + (300-x)0.15=38

after the solving the equation ,,x=140
Manager
Joined: 19 Dec 2010
Posts: 72

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11 Mar 2011, 04:15
This problem is relatively easy once you break it up the way it's supposed to be broken up...

they basically say X lbs +Y lbs = 300 lbs

Now, equate the protein levels together:

0.10 X + 0.15 Y = 38

Solve
Manager
Joined: 25 May 2011
Posts: 92
Re: A rabbit on a controlled diet is fed daily 300 grams of a  [#permalink]

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07 Nov 2011, 02:47
just calculation:

0.1*X+0.15*(300-X)=38
X=140
Manager
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Re: A rabbit on a controlled diet is fed daily 300 grams of a  [#permalink]

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17 Aug 2015, 00:40
1
we can solve by testing answers
let qty of X be 140 gms. so Y will be 160 gms.
proteins from X = 14 gms
proteins from Y = 24 gms

so X must be 140 gms.
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Re: A rabbit on a controlled diet is fed daily 300 grams of a  [#permalink]

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01 Feb 2016, 22:30
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30 sec reasoning out: 38/300 - is a bit less than a 13% protein content. Hence 13% is closer to 15%Y than to 10%X - this means that there is just sligthly more Y component because should those 2 be equal the protein content would have been sharply 12.5% which is not the case.

Immediately we kick out 3 answer choices >= 150 and are left with A and B. A is too low for the aboe slight deviation - so B is much closer to truth.
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A rabbit on a controlled diet is fed daily 300 grams of a  [#permalink]

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01 Feb 2016, 22:53
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30 sec reasoning out: 38/300 - is a bit less than a 13% protein content. Hence 13% is closer to 15%Y than to 10%X - this means that there is just sligthly more Y component because should those 2 be equal the protein content would have been sharply 12.5% which is not the case.

Immediately we kick out 3 answer choices >= 150 and are left with A and B. A is too low for the aboe slight deviation - so B is much closer to truth.

Hi,
this weighted approach,if mastered, can actually make a difference in your Quant score..
Good approach and you should try this in almost all Q that asks for an average in a mixture, or for a quantity, when an average is given..
+1 kudos
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Re: A rabbit on a controlled diet is fed daily 300 grams of a  [#permalink]

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01 Feb 2016, 23:14
1
1
I am going through word problem types of questions because I think i bombed this type of q in my last gmat both time-wise and accuracy wise. And what i see from OG about 30% of all questions comprise the word problem type.

During these 2 days I solved numerous word problems and here are my observations:

- very time consuming because the intuitive approach is to apply algebra and form equations, on average easy question take almost the same time as hard ones
- given my incline to make silly mistakes in algebraic calculations I should rely more on reasoning out the easy questions
- majority of easy word problems employ weighted average or mean concepts which can be done by reasoning much faster than by doing algebra - ultimately this will save at least 30 secs on each such question
-
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A rabbit on a controlled diet is fed daily 300 grams of a  [#permalink]

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26 Mar 2016, 17:25
Here is a visual that should help.
Attachments

Screen Shot 2016-03-26 at 6.26.43 PM.png [ 108.49 KiB | Viewed 23307 times ]

Manager
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Re: A rabbit on a controlled diet is fed daily 300 grams of a  [#permalink]

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23 May 2016, 11:29
The answer choices are wide enough to narrow down. Food X < average, therefore options C to D are out. Can't be 100 because it is to far away from the average, hence B.

tinman1412 wrote:
A rabbit on a controlled diet is fed daily 300 grams of a mixture of two foods, food X and food Y. Food X contains 10% protein and food Y contains 15% protein. If the rabbit's diet provides exactly 38 grams of protein daily, how many grams of food X are in the mixture.

A. 100
B. 140
C. 150
D. 160
E. 200
Manager
Joined: 23 Feb 2015
Posts: 165
Schools: Duke '19 (M)
Re: A rabbit on a controlled diet is fed daily 300 grams of a  [#permalink]

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23 May 2016, 11:52
$$.1x+.15(300-x)=38$$

$$10x+4500-15x=3800$$

$$5x=700$$

$$x=140$$
Re: A rabbit on a controlled diet is fed daily 300 grams of a   [#permalink] 23 May 2016, 11:52

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