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

 It is currently 21 Oct 2018, 20:43

### 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

# M18-21

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50009

### Show Tags

16 Sep 2014, 01:04
00:00

Difficulty:

15% (low)

Question Stats:

80% (01:14) correct 20% (01:30) wrong based on 189 sessions

### HideShow timer Statistics

If a 30%-solution of alcohol was mixed with a 50%-solution of alcohol to obtain 10 liters of a 45%-solution of alcohol, how much of the 30%-solution was used?

A. 2.0 liters
B. 2.5 liters
C. 2.7 liters
D. 3.0 liters
E. 3.2 liters

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 50009

### Show Tags

16 Sep 2014, 01:04
Official Solution:

If a 30%-solution of alcohol was mixed with a 50%-solution of alcohol to obtain 10 liters of a 45%-solution of alcohol, how much of the 30%-solution was used?

A. 2.0 liters
B. 2.5 liters
C. 2.7 liters
D. 3.0 liters
E. 3.2 liters

Say there are $$x$$ liters of a 30%-solution of alcohol then there would be $$10-x$$ liters of a 50%-solution of alcohol.

Equate the amount of alcohol in 10 liters of mixture $$0.3x+0.5(10-x)=0.45*10$$, which gives $$x=2.5$$ liters.

_________________
Current Student
Joined: 06 Mar 2014
Posts: 247
Location: India
GMAT Date: 04-30-2015

### Show Tags

27 Sep 2014, 07:31
1
Bunuel wrote:
Official Solution:

If a 30%-solution of alcohol was mixed with a 50%-solution of alcohol to obtain 10 liters of a 45%-solution of alcohol, how much of the 30%-solution was used?

A. 2.0 liters
B. 2.5 liters
C. 2.7 liters
D. 3.0 liters
E. 3.2 liters

Say there are $$x$$ liters of a 30%-solution of alcohol then there would be $$10-x$$ liters of a 45%-solution of alcohol.

Equate the amount of alcohol in 10 liters of mixture $$0.3x+0.5(10-x)=0.45*10$$, which gives $$x=2.5$$ liters.

Bunuel,

Kindly correct me if i am wrong but isn't 50% solution of alcohol supposed to come in the above highlighted section.
ie: there would be $$10-x$$ liters of a 50%-solution of alcohol.
Math Expert
Joined: 02 Sep 2009
Posts: 50009

### Show Tags

27 Sep 2014, 13:09
earnit wrote:
Bunuel wrote:
Official Solution:

If a 30%-solution of alcohol was mixed with a 50%-solution of alcohol to obtain 10 liters of a 45%-solution of alcohol, how much of the 30%-solution was used?

A. 2.0 liters
B. 2.5 liters
C. 2.7 liters
D. 3.0 liters
E. 3.2 liters

Say there are $$x$$ liters of a 30%-solution of alcohol then there would be $$10-x$$ liters of a 45%-solution of alcohol.

Equate the amount of alcohol in 10 liters of mixture $$0.3x+0.5(10-x)=0.45*10$$, which gives $$x=2.5$$ liters.

Bunuel,

Kindly correct me if i am wrong but isn't 50% solution of alcohol supposed to come in the above highlighted section.
ie: there would be $$10-x$$ liters of a 50%-solution of alcohol.

Typo edited. Thank you.
_________________
Intern
Joined: 05 Feb 2017
Posts: 2

### Show Tags

16 Feb 2017, 12:23
It can be useful to think in terms of a picture to solve this

30% 35% 40% 45% 50%
0----1----2----3----4

the ratio of space between 30% - 45% and 45% to 50% is 3:1

45% is closer to 50% than to 30 %, so there is 3 times as much 50% solution mixed in as there is 30% solution

so for every 4 litres added, 1L will be 30% solution
(1/4) * 10 L = 2.5L

Hopefully this helps
Re: M18-21 &nbs [#permalink] 16 Feb 2017, 12:23
Display posts from previous: Sort by

# M18-21

Moderators: chetan2u, Bunuel

 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®.