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

 It is currently 22 Feb 2019, 06:47

### 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

## Events & Promotions

###### Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
• ### Free GMAT RC Webinar

February 23, 2019

February 23, 2019

07:00 AM PST

09:00 AM PST

Learn reading strategies that can help even non-voracious reader to master GMAT RC. Saturday, February 23rd at 7 AM PT
• ### FREE Quant Workshop by e-GMAT!

February 24, 2019

February 24, 2019

07:00 AM PST

09:00 AM PST

Get personalized insights on how to achieve your Target Quant Score.

# How much pure alcohol should be added to 400ml of a 15% solu

Author Message
TAGS:

### Hide Tags

Manager
Joined: 22 Jul 2008
Posts: 80
Location: Bangalore,Karnataka
How much pure alcohol should be added to 400ml of a 15% solu  [#permalink]

### Show Tags

02 Dec 2009, 00:21
2
9
00:00

Difficulty:

15% (low)

Question Stats:

82% (02:01) correct 18% (02:25) wrong based on 297 sessions

### HideShow timer Statistics

How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 32%?

A. 100 ml
B. 60 ml
C. 120 ml
D. 130 ml
E. 150 ml
Senior Manager
Joined: 30 Aug 2009
Posts: 269
Location: India
Concentration: General Management

### Show Tags

02 Dec 2009, 00:35
1
kirankp wrote:
How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 32%?

A)100 ml
B) 60 ml
C)120 ml
D)130 ml
E)150 ml

400ml has 15% alcohol i.e 60ml . This means we have 340ml of water or the liquid with which alcohol is mixed
Let V be the volume of alcohol added to make the strength 32%
then V/340+V = 32/100. solving this we get V as 160ml

so we need to add 160 -60 = 100ml of alcohol

A-100ml
Intern
Joined: 31 Oct 2009
Posts: 27

### Show Tags

02 Dec 2009, 13:28
3
Here's how I did it:

$$(400)(.15) = 60$$ mL of Alcohol

$$.32 = \frac{60+x}{400+x}$$

$$(.32)(400+x)=60+x$$

$$128+.32x=60+x$$

$$68=.68x$$

$$x=100$$
Manager
Joined: 13 Aug 2009
Posts: 117
WE 1: 4 years in IT

### Show Tags

02 Dec 2009, 22:17
we can also go by answer choices

Tke 100 ml for eg

400 (old)+100 (new concentr)ml

500*32/100 = 160 ml (60ml is de old concentration +100 ml (newly added)

Let me know if im wrong

Cheers,
Raghav
Senior Manager
Joined: 30 Aug 2009
Posts: 269
Location: India
Concentration: General Management

### Show Tags

02 Dec 2009, 22:25
raghavs wrote:
we can also go by answer choices

Tke 100 ml for eg

400 (old)+100 (new concentr)ml

500*32/100 = 160 ml (60ml is de old concentration +100 ml (newly added)

Let me know if im wrong

Cheers,
Raghav

yes we can go by answer choices as well....but in GMAT we will see questions having values either in ascending or descending order unlike the options in the question here. Plugging in/POE is always suggested to be done taking the middle option first and then proceed.
I feel taking answer choices will take more time to solve this question.
Manager
Joined: 09 May 2009
Posts: 178

### Show Tags

17 Dec 2009, 03:23
1
kirankp wrote:
How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 32%?

A)100 ml
B) 60 ml
C)120 ml
D)130 ml
E)150 ml

15% of 400=60 ml
(60+x)/(400+x)=32%
solving x=100 ml
_________________

GMAT is not a game for losers , and the moment u decide to appear for it u are no more a loser........ITS A BRAIN GAME

Senior SC Moderator
Joined: 22 May 2016
Posts: 2491
How much pure alcohol should be added to 400ml of a 15% solu  [#permalink]

### Show Tags

19 Dec 2017, 13:45
kirankp wrote:
How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 32%?

A. 100 ml
B. 60 ml
C. 120 ml
D. 130 ml
E. 150 ml

Let x = the amount of alcohol to be added
x = 100% alcohol = 1.00 (decimal percent)

Weighted average, slight variation.
For each part, A and B, to be mixed:

1) multiply its alcohol concentration (weight) by its volume

2) sum the separate results, which =

3) (Desired alcohol concentration of resultant solution) * (Volume of resultant solution, usually A + B)

.15(400) + 1(x) = .32(400 + x)

60 + x = 128 + .32x

.68x = 68

x = $$\frac{68}{.68}= 100$$

_________________

To live is the rarest thing in the world.
Most people just exist.

Oscar Wilde

Intern
Joined: 16 Jul 2016
Posts: 39
Re: How much pure alcohol should be added to 400ml of a 15% solu  [#permalink]

### Show Tags

19 Dec 2017, 13:59
1
Method 1:
Equation in terms of alcohol.
400(.15)+x(1.0)=(400+x)(.32)

60+x=128+.32x
.68x=68
x=100

Method 2: Equation in terms of water

.85(400)+x(0)=(.68)(400+x)

solving for x will give you the same answer.

Method 3- alligation

15____________32_____________100

68 17

4 1

the ratio of the 15 percent solution to pure alcohol = 4:1
Since there are 400 ml of the 15% solution, the multiplier is 100. 100(1)=100
Intern
Joined: 16 Jul 2016
Posts: 39
How much pure alcohol should be added to 400ml of a 15% solu  [#permalink]

### Show Tags

19 Dec 2017, 14:00
Method 1:

Equation in terms of alcohol.

400(.15)+x(1.0)=(400+x)(.32)

60+x=128+.32x

.68x=68

x=100

Method 2: Equation in terms of water

.85(400)+x(0)=(.68)(400+x)

solving for x will give you the same answer.

Method 3- alligation

15____________32_____________100

68__________________________________ 17

4 _________________________________ 1

the ratio of the 15 percent solution to pure alcohol = 4:1
Since there are 400 ml of the 15% solution, the multiplier is 100. 100(1)=100

Method 4-Weighted average (in terms of alcohol)

[400(.15)+x]/[400+x]=32/100

Method 5-Weighted average (in terms of water)

[400(.85)]/[400+x]=68/100
VP
Joined: 07 Dec 2014
Posts: 1154
Re: How much pure alcohol should be added to 400ml of a 15% solu  [#permalink]

### Show Tags

19 Dec 2017, 17:43
kirankp wrote:
How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 32%?

A. 100 ml
B. 60 ml
C. 120 ml
D. 130 ml
E. 150 ml

.15*400+a=.32(400+a)
a=100 ml
A
Manager
Joined: 22 Sep 2018
Posts: 246
Re: How much pure alcohol should be added to 400ml of a 15% solu  [#permalink]

### Show Tags

22 Jan 2019, 16:03
kirankp wrote:
How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 32%?

A. 100 ml
B. 60 ml
C. 120 ml
D. 130 ml
E. 150 ml

I felt that using allegation was the easiest way to solve this question.

We need the solutions to be mixed in a 4:1 ratio, thus if we have 400ml of the first mixture, we will need 100ml of pure alcohol to make a mixture with ratio 4:1.
Re: How much pure alcohol should be added to 400ml of a 15% solu   [#permalink] 22 Jan 2019, 16:03
Display posts from previous: Sort by