GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 18 Aug 2018, 15:00

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# M07-28

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 47983

### Show Tags

16 Sep 2014, 00:35
00:00

Difficulty:

55% (hard)

Question Stats:

67% (02:16) correct 33% (02:18) wrong based on 48 sessions

### HideShow timer Statistics

To make lemonade, a recipe requires 4 lemons, 30 ounces of sugar, and 2 pints of water. From an average lemon one can squeeze out 0.4 cups of 5% citric acid. Marta does not have lemons, but wants to make lemonade from 4 cups of 12% citric acid. If she has sugar and water in abundance, how much water will Marta use?

A. 2 pt.
B. 6 pt.
C. 12 pt.
D. 15 pt.
E. 100 pt.

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 47983

### Show Tags

16 Sep 2014, 00:35
1
2
Official Solution:

To make lemonade, a recipe requires 4 lemons, 30 ounces of sugar, and 2 pints of water. From an average lemon one can squeeze out 0.4 cups of 5% citric acid. Marta does not have lemons, but wants to make lemonade from 4 cups of 12% citric acid. If she has sugar and water in abundance, how much water will Marta use?

A. 2 pt.
B. 6 pt.
C. 12 pt.
D. 15 pt.
E. 100 pt.

Standard recipe requires: 4 lemons and 2 pints of water. 4 lemons contain $$4*0.4*\frac{5}{100}=\frac{8}{100}$$ cups of citric acid;

Now, Marta has $$4*\frac{12}{100}=\frac{48}{100}$$ cups of citric acid, so 6 times as many as the standard recipe requires ($$\frac{48}{8}=6$$), which means that she'll need 6 times as much water as the standard recipe requires. Hence she'll need $$6*2=12$$ pints of water.

_________________
Retired Moderator
Joined: 29 Apr 2015
Posts: 862
Location: Switzerland
Concentration: Economics, Finance
Schools: LBS MIF '19
WE: Asset Management (Investment Banking)

### Show Tags

15 Jun 2015, 12:09
Bunuel wrote:
Official Solution:

To make lemonade, a recipe requires 4 lemons, 30 ounces of sugar, and 2 pints of water. From an average lemon one can squeeze out 0.4 cups of 5% citric acid. Marta does not have lemons, but wants to make lemonade from 4 cups of 12% citric acid. If she has sugar and water in abundance, how much water will Marta use?

A. 2 pt.
B. 6 pt.
C. 12 pt.
D. 15 pt.
E. 100 pt.

Standard recipe requires: 4 lemons and 2 pints of water. 4 lemons contain $$4*0.4*\frac{5}{100}=\frac{8}{100}$$ cups of citric acid;

Now, Marta has $$4*\frac{12}{100}=\frac{48}{100}$$ cups of citric acid, so 6 times as many as the standard recipe requires ($$\frac{48}{8}=6$$), which means that she'll need 6 times as much water as the standard recipe requires. Hence she'll need $$6*2=12$$ pints of water.

Can we start a discussion here and revive this task here a bit with the following questions?

Since this is a mixture problem, how do we account for the different percentages of citric acid? I do not see this in the answer, it's not clear for me.

The recipe requires 4 lemons i.e. 4*0.4 cups * 5%? Does this mean, the recipe requires 8 of what... (what? what's the measure after doing the calculations )
_________________

Saving was yesterday, heat up the gmatclub.forum's sentiment by spending KUDOS!

PS Please send me PM if I do not respond to your question within 24 hours.

Intern
Joined: 09 Feb 2015
Posts: 7

### Show Tags

25 Jun 2015, 01:25
yes please expain why did u convert the % concentration in to number of cups
Intern
Joined: 09 Feb 2015
Posts: 20

### Show Tags

12 Jul 2015, 22:52
My solution:
Given: Lemon one: 0.4*5/100 = 1/50 (citric acid)
4 cups of 12% citric acid = 4*12/100 = 12/25 = 24/50 (citric acid)
=> We have 24 lemons from 4 cups of 12% citric acid. 24/4 = 6 cups.
=> Pints of water: 6*2 = 12.
Is it right?
Intern
Joined: 06 May 2016
Posts: 14

### Show Tags

06 Sep 2016, 13:01
Bunuel wrote:
To make lemonade, a recipe requires 4 lemons, 30 ounces of sugar, and 2 pints of water. From an average lemon one can squeeze out 0.4 cups of 5% citric acid. Marta does not have lemons, but wants to make lemonade from 4 cups of 12% citric acid. If she has sugar and water in abundance, how much water will Marta use?

A. 2 pt.
B. 6 pt.
C. 12 pt.
D. 15 pt.
E. 100 pt.

Bunuel,

Need to your help in understanding where I am doing the mistake:

i am converting everything in to 5% concentrate

lets find how much of water will be required to convert the 12% to 5% concentration

12 ---- 0 (pure water)
v
5 .
^
5--------7

5/7= 4/x x= 5.6 pints of water is required to dilute the 12% 4 cups to 5% concentration.

now, 1 lemon can have 0.4 cups of 5% of citric acid, so 4 *0.4 =1.6 cup

so 1. 6 cup require 2 pints of water for actual recipe. So we have 4 cups(already diluted 12% to 5%) will require 5 pints of water
so total water required is 5.6 +5 ==>10.6 (not listed though!)
Intern
Joined: 15 Oct 2016
Posts: 1

### Show Tags

13 Jun 2017, 02:54
In this case , we dont have to use the standard Part/whole = % formula that is commonly used in mixtures problems.

Here the question first provides standard lemonade recipe - 4 lemons, 30 ounces of sugar and 2 pints of water. -- (A)
Since question asks for water requirement, we can ignore the sugar content. So, standard recipe says for 4 lemons , we need 2 pints of water. We also understand that One Lemon = 0.4 cups of 5% citric acid. (B)

Correlating (A) and (B), we understand that in a standard lemonade recipe , we will use 1.6 cups of 5% citric acid with 2 pints of water.

From now on, the question is purely relations...

If 1.6 Cups of 5% citric acid -------> 2 pints ,
then 1.6 cups of 12% citric acid ------> X
Using inversion, 5x = 12*2 , solving for x , we get x = 4.8 pints. So, if we had the same 1.6 cups of higher concentration citric acid ( 12%), then we need more water i.e 4.8 pints.

Now, the final step ,

If 1.6 cups of 12% citric acid requires 4.8 pints of water, then how much will 4 cups of 12% citric acid require .

Applying same relation , 1.6 x = 4.8 * 4, solving for x we will get 12 pints , the answer
Intern
Joined: 08 Dec 2016
Posts: 40

### Show Tags

30 Dec 2017, 13:35
I think this is a high-quality question and I agree with explanation. Take into consideration the quantity, concentration, and water. The proportion of concetration must be keep the same. Therefore we have the equation:

L*0.4*(5%)/2pt = 4*(12%)/X

X=12
Intern
Joined: 30 Jan 2018
Posts: 2

### Show Tags

10 Feb 2018, 14:37
Why would we assume that all 4 cups of the 12% acid needs to be used. We only need to dilute 1 cup to get a 5% mixture (12%>5%). Why would Martha not use 1 cup of the 12% mixture to get the 5% diluted acid? Clearly the answer has choices which require all 4 but that would take some time to figure out. This is a high quality question. I wish the question had specified that we need to use all 4 cups of the acid for dilution.
M07-28 &nbs [#permalink] 10 Feb 2018, 14:37
Display posts from previous: Sort by

# M07-28

Moderators: chetan2u, Bunuel

# Events & Promotions

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.