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

 It is currently 18 Oct 2019, 10:08

### 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

# How many ounces of water must be added to 10 ounces of 3 % alcohol

Author Message
TAGS:

### Hide Tags

Senior Manager
Joined: 25 Sep 2018
Posts: 426
Location: United States (CA)
Concentration: Finance, Strategy
GMAT 1: 640 Q47 V30
GPA: 3.97
WE: Investment Banking (Investment Banking)
How many ounces of water must be added to 10 ounces of 3 % alcohol  [#permalink]

### Show Tags

01 Oct 2018, 03:48
3
00:00

Difficulty:

15% (low)

Question Stats:

81% (01:21) correct 19% (01:32) wrong based on 70 sessions

### HideShow timer Statistics

How many ounces of water must be added to 10 ounces of 3 % alcohol and water solution to reduce the solution to 1 % alcohol.
A)5
B)10
C)15
D)20
E)30

_________________
Why do we fall?...So we can learn to pick ourselves up again
CEO
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2978
Location: India
GMAT: INSIGHT
Schools: Darden '21
WE: Education (Education)
Re: How many ounces of water must be added to 10 ounces of 3 % alcohol  [#permalink]

### Show Tags

01 Oct 2018, 04:03
1
1
Abhi077 wrote:
How many ounces of water must be added to 10 ounces of 3 % alcohol and water solution to reduce the solution to 1 % alcohol.
A)5
B)10
C)15
D)20
E)30

Alchohol Quantity = (3/100)*10 = 0.3 Ounce

Now, After adding water the same alcohol quantity should represent 1% of the total new quantity

i.e. $$0.3 = (1/100)*(10+x)$$ . where $$x$$ is the quantity of water added

i.e. $$10+x = 30$$

i.e. $$x = 20$$

_________________
Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com I Call us : +91-9999687183 / 9891333772
Online One-on-One Skype based classes and Classroom Coaching in South and West Delhi
http://www.GMATinsight.com/testimonials.html

ACCESS FREE GMAT TESTS HERE:22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION
Manager
Joined: 21 Nov 2016
Posts: 70
GMAT 1: 640 Q47 V31
Re: How many ounces of water must be added to 10 ounces of 3 % alcohol  [#permalink]

### Show Tags

01 Oct 2018, 04:15
1
Let x be the no. of ounces of water to be added.
We know that 10 ounces of solution has 3% alcohol. That is 10*(3/100) = 0.3 ounces. So, 10 ounces of solution consists of 0.3 ounces of alcohol and 9.7 ounces of water.
Now, with the above information, since there is no addition of alcohol , the amount of alcohol in the resultant solution after addition of water will be the same 0.3 ounces. But, the percentage will change to 1%.
So, 0.3 = (10+x)(1/100)
Implies, 0.3 = 1/10 +x/100
0.3 = (10+x)/100
30 = 10 + x
x = 20.
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 4009
Re: How many ounces of water must be added to 10 ounces of 3 % alcohol  [#permalink]

### Show Tags

03 Oct 2018, 10:52
1
Top Contributor
Abhi077 wrote:
How many ounces of water must be added to 10 ounces of 3 % alcohol and water solution to reduce the solution to 1 % alcohol.
A)5
B)10
C)15
D)20
E)30

The original solution contains 10 ounces
3% of that is alcohol
3% of 10 = 0.3
So, the original solution contains 0.3 ounces of alcohol

Let x = the amount of water (in ounces) that must be added
So, the volume of the RESULTING solution = 10 + x ounces

IMPORTANT: Since we're adding water only, the volume of alcohol does not change.
In other words, there are 0.3 ounces of alcohol in the RESULTING solution

We want the RESULTING solution to be 1% alcohol
In other words: (volume of alcohol in solution)/(total volume of solution) = 1/100
Rewrite as: 0.3 /(10 + x) = 1/100
Multiply both sides by (10 + x) to get: 0.3 = (10 + x)/100
Multiply both sides by 100 to get: 30 = 10 + x
Solve: x = 20

RELATED VIDEO FROM OUR COURSE

_________________
Test confidently with gmatprepnow.com
GMATH Teacher
Status: GMATH founder
Joined: 12 Oct 2010
Posts: 935
Re: How many ounces of water must be added to 10 ounces of 3 % alcohol  [#permalink]

### Show Tags

03 Oct 2018, 11:17
Abhi077 wrote:
How many ounces of water must be added to 10 ounces of 3 % alcohol and water solution to reduce the solution to 1 % alcohol.
A)5
B)10
C)15
D)20
E)30

Let´s do it with another technique: alligation!

$$? = x$$

$${{10} \over {10 + x}} = {{1 - 0} \over {3 - 0}}\,\,\left( { = {{10} \over {30}}} \right)\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,? = 20$$

This solution follows the notations and rationale taught in the GMATH method.

Regards,
Fabio.
_________________
Fabio Skilnik :: GMATH method creator (Math for the GMAT)
Our high-level "quant" preparation starts here: https://gmath.net
Re: How many ounces of water must be added to 10 ounces of 3 % alcohol   [#permalink] 03 Oct 2018, 11:17
Display posts from previous: Sort by