Last visit was: 12 Jul 2025, 09:45 It is currently 12 Jul 2025, 09:45
Close
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
Your Progress

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
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Close
Request Expert Reply
Confirm Cancel
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 11 Jul 2025
Posts: 102,636
Own Kudos:
Given Kudos: 98,172
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 102,636
Kudos: 740,708
 [10]
Kudos
Add Kudos
10
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
quantumliner
Joined: 24 Apr 2016
Last visit: 26 Sep 2018
Posts: 244
Own Kudos:
752
 [9]
Given Kudos: 48
Posts: 244
Kudos: 752
 [9]
6
Kudos
Add Kudos
3
Bookmarks
Bookmark this Post
General Discussion
User avatar
KrishnakumarKA1
Joined: 05 Jan 2017
Last visit: 13 Oct 2020
Posts: 403
Own Kudos:
302
 [1]
Given Kudos: 15
Location: India
Posts: 403
Kudos: 302
 [1]
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
User avatar
EugeneFish
Joined: 19 Jul 2016
Last visit: 09 Dec 2020
Posts: 12
Own Kudos:
115
 [3]
Given Kudos: 51
Location: Moldova, Republic of
Concentration: Strategy, Operations
Posts: 12
Kudos: 115
 [3]
1
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
If we add 10 oz of 100% solution, we will have a 60% mixture. Answer A out
If we add 20 oz of 100% solution, we will have an 80% mixture. Answer B out.

Further, we can use weighted average :

40---------------88------100

Distance between 88 and 40 is 48
Distance between 88 and 100 is 12

Ratio of 40% sol to 100% sol in the mixture is 12:48 or 1:4
So, the mixture will consist of 1 ratio unit of 40% sol and 4 ratio units of 100% sol. One ratio unit is 10, therefore 4 x 10 = 40.
Answer D
User avatar
gracie
Joined: 07 Dec 2014
Last visit: 11 Oct 2020
Posts: 1,035
Own Kudos:
1,859
 [1]
Given Kudos: 27
Posts: 1,035
Kudos: 1,859
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
A solution that is 40% acid must be strengthened to become a solution that is 88% acid. If there are 10 ounces of the 40% solution, how much pure acid must be added?

A. 2.5 ounces
B. 18 ounces
C. 28 ounces
D. 40 ounces
E. 48 ounces

let x=ounces of acid to be added
.4*10+x=.88(10+x)
x=40 ounces
D
User avatar
akshayk
Joined: 06 Jul 2016
Last visit: 21 Sep 2020
Posts: 273
Own Kudos:
402
 [4]
Given Kudos: 99
Location: Singapore
Concentration: Strategy, Finance
Posts: 273
Kudos: 402
 [4]
2
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
Bunuel
A solution that is 40% acid must be strengthened to become a solution that is 88% acid. If there are 10 ounces of the 40% solution, how much pure acid must be added?

A. 2.5 ounces
B. 18 ounces
C. 28 ounces
D. 40 ounces
E. 48 ounces

We need to make 40% acid solution into a 88% acid solution.

A1 = 40% Acid Solution
A2 = 100% Acid Solution (Pure Acid)
Final = 88% Acid Solution

A1:A2 = 1:4
If we have 10 ounces of A1, we need to have 40 ounces of A2.

Hence D :)

Thank you Karishma for the weighted average method.
avatar
Shtan1
Joined: 22 Sep 2016
Last visit: 07 Jan 2018
Posts: 1
Given Kudos: 1
Posts: 1
Kudos: 0
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Ballparking, 48 is impossible because the acidic will be more than 88%, a little lesser than 48, which is 40 Answer D.
User avatar
ccooley
User avatar
Manhattan Prep Instructor
Joined: 04 Dec 2015
Last visit: 06 Jun 2020
Posts: 931
Own Kudos:
Given Kudos: 115
GMAT 1: 790 Q51 V49
GRE 1: Q170 V170
Expert
Expert reply
GMAT 1: 790 Q51 V49
GRE 1: Q170 V170
Posts: 931
Kudos: 1,620
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
A solution that is 40% acid must be strengthened to become a solution that is 88% acid. If there are 10 ounces of the 40% solution, how much pure acid must be added?

A. 2.5 ounces
B. 18 ounces
C. 28 ounces
D. 40 ounces
E. 48 ounces

I'd test the answer choices (possibly with a bit of estimation) on this one. The answer choices are easy numbers, while the math will require some algebra, so let's make it easier on ourselves.

Initially, we have 10 ounces of the solution, and .4(10) = 4 ounces of that consists of acid.

Start by testing (B): if we add 18 ounces of acid, we now have a total of 10+18 = 28 ounces of solution, and 4 + 18 = 22 ounces of that is acid.

How does 22/28 compare to 88%? It looks like we need an easy way to compare 88% to a bunch of different fractions, so let's convert 88% to a fraction as well: 88% = 88/100 = 22/25.

22/28 has a bigger denominator than 22/25, and the same numerator. Therefore, 22/28 is too small and we need to test a bigger answer choice.

Next, test (D): if we add 40 ounces of acid, we have a total of 10 + 40 = 50 ounces of solution, and 4 + 40 = 44 ounces of that is acid.

44/50 = 88/100 = 88%. The correct answer is (D).
User avatar
warrior1991
Joined: 03 Mar 2017
Last visit: 03 Feb 2022
Posts: 573
Own Kudos:
Given Kudos: 596
Location: India
Concentration: Operations, Technology
Products:
Posts: 573
Kudos: 433
Kudos
Add Kudos
Bookmarks
Bookmark this Post
chetan2u Bunuel

What do we mean by 10 ounces of 40% solution ??

I was assuming that 40% solution has 10 ounces

So 100% solution will have 25 ounces.

Total Solution has 25 ounces out of which acid is 40% and that again means 10 ounces of acid and remaining 15 ounces of water.

Now this 25 ounces has to be increased by adding acid such that the acid content is 88%.

(10+x)/(25+x)=88/100

On solving X comes out to be 100.

That means we need to add 100 ounces of acid .

Where am I wrong??
User avatar
chetan2u
User avatar
GMAT Expert
Joined: 02 Aug 2009
Last visit: 12 Jul 2025
Posts: 11,295
Own Kudos:
Given Kudos: 333
Status:Math and DI Expert
Products:
Expert
Expert reply
Posts: 11,295
Kudos: 41,698
Kudos
Add Kudos
Bookmarks
Bookmark this Post
warrior1991
chetan2u Bunuel

What do we mean by 10 ounces of 40% solution ??

I was assuming that 40% solution has 10 ounces

So 100% solution will have 25 ounces.

Total Solution has 25 ounces out of which acid is 40% and that again means 10 ounces of acid and remaining 15 ounces of water.

Now this 25 ounces has to be increased by adding acid such that the acid content is 88%.

(10+x)/(25+x)=88/100

On solving X comes out to be 100.

That means we need to add 100 ounces of acid .

Where am I wrong??

Hi,

10 ml of 40% solution...This means the solution is a mix of 40% of acid etc and 60% of water, and we are taking 10ml of it, so acid will be 4ml
User avatar
warrior1991
Joined: 03 Mar 2017
Last visit: 03 Feb 2022
Posts: 573
Own Kudos:
Given Kudos: 596
Location: India
Concentration: Operations, Technology
Products:
Posts: 573
Kudos: 433
Kudos
Add Kudos
Bookmarks
Bookmark this Post
chetan2u
warrior1991
chetan2u Bunuel

What do we mean by 10 ounces of 40% solution ??

I was assuming that 40% solution has 10 ounces

So 100% solution will have 25 ounces.

Total Solution has 25 ounces out of which acid is 40% and that again means 10 ounces of acid and remaining 15 ounces of water.

Now this 25 ounces has to be increased by adding acid such that the acid content is 88%.

(10+x)/(25+x)=88/100

On solving X comes out to be 100.

That means we need to add 100 ounces of acid .

Where am I wrong??

Hi,

10 ml of 40% solution...This means the solution is a mix of 40% of acid etc and 60% of water, and we are taking 10ml of it, so acid will be 4ml


Thank you chetan2u for a quick response. You mean to say that 40% solution and 10 ml means same thing??? Because it is already given that solution has 40% acid and 60% of water.
User avatar
satya2029
Joined: 10 Dec 2017
Last visit: 12 Jul 2025
Posts: 231
Own Kudos:
Given Kudos: 136
Location: India
Posts: 231
Kudos: 241
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
A solution that is 40% acid must be strengthened to become a solution that is 88% acid. If there are 10 ounces of the 40% solution, how much pure acid must be added?

A. 2.5 ounces
B. 18 ounces
C. 28 ounces
D. 40 ounces
E. 48 ounces
Initial quantity of acid=40% of 10=4 ounces
Final quantity of acid= 4+x(added acid)
Which is equal to 88% of( 10+added acid)
so (4+x)=0.88(10+x)
X=40 ounces
D:)
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 37,374
Own Kudos:
Posts: 37,374
Kudos: 1,010
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Moderators:
Math Expert
102636 posts
PS Forum Moderator
688 posts