Last visit was: 24 Apr 2026, 04:30 It is currently 24 Apr 2026, 04:30
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
mangamma
Joined: 25 Dec 2018
Last visit: 12 Jul 2023
Posts: 505
Own Kudos:
1,872
 [6]
Given Kudos: 994
Location: India
Concentration: General Management, Finance
GMAT Date: 02-18-2019
GPA: 3.4
WE:Engineering (Consulting)
Posts: 505
Kudos: 1,872
 [6]
Kudos
Add Kudos
6
Bookmarks
Bookmark this Post
User avatar
Lampard42
Joined: 22 Nov 2018
Last visit: 12 Dec 2020
Posts: 424
Own Kudos:
Given Kudos: 292
Location: India
GMAT 1: 640 Q45 V35
GMAT 2: 740 Q49 V41
GMAT 2: 740 Q49 V41
Posts: 424
Kudos: 561
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
pushpitkc
Joined: 26 Feb 2016
Last visit: 19 Feb 2025
Posts: 2,800
Own Kudos:
6,235
 [4]
Given Kudos: 47
Location: India
GPA: 3.12
Posts: 2,800
Kudos: 6,235
 [4]
Kudos
Add Kudos
3
Bookmarks
Bookmark this Post
User avatar
GMATWhizTeam
User avatar
GMATWhiz Representative
Joined: 07 May 2019
Last visit: 17 Mar 2026
Posts: 3,374
Own Kudos:
Given Kudos: 70
Location: India
GMAT 1: 740 Q50 V41
GMAT 2: 760 Q51 V40
Expert
Expert reply
GMAT 2: 760 Q51 V40
Posts: 3,374
Kudos: 2,193
Kudos
Add Kudos
Bookmarks
Bookmark this Post
mangamma
A class in a certain school consists of boys and girls in the ratio of 2:1. In a mathematics test, 60% of the class passed the test. If 40% of the boys failed the test, what percentage of the class are girls who passed the test?


A. 10%
B. 20%
C. 30%
D. 40%
E. 60%

Solution


    • Let us assume that there are total 30 student in the class.
    • Now, based on the information given in the question, let us make the following tree-structure:

    • From the above tree structure, the percent of girls who passed the mathematics test out of the total class \(= \frac{6}{30}*100 = 20\)%
Thus, the correct answer is Option B.
User avatar
Sabby
Joined: 17 Jun 2018
Last visit: 04 Mar 2026
Posts: 84
Own Kudos:
Given Kudos: 397
Location: France
GPA: 3.85
Posts: 84
Kudos: 118
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hi,
We have 2/3 boys, or let's say 20/30 boys and 10/30 girls

2/3*4/10= 8/30 boys who failed
which means we have 4/10 or 12/30-8/30= 4/30 girls who failed
Therefore we have 6/30 girls who passed : 2/10 or 20/100

Answer B)
User avatar
CEdward
Joined: 11 Aug 2020
Last visit: 14 Apr 2022
Posts: 1,162
Own Kudos:
Given Kudos: 332
Posts: 1,162
Kudos: 289
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I assumed the total # in the class was 120. I got 7/30 in the end. Can someone see the attachment and let me know where I went wrong? Should be 6/30 = 20%.
Attachments

classroom.docx [12.17 KiB]
Downloaded 79 times

User avatar
Sabby
Joined: 17 Jun 2018
Last visit: 04 Mar 2026
Posts: 84
Own Kudos:
Given Kudos: 397
Location: France
GPA: 3.85
Posts: 84
Kudos: 118
Kudos
Add Kudos
Bookmarks
Bookmark this Post
CEdward
I assumed the total # in the class was 120. I got 7/30 in the end. Can someone see the attachment and let me know where I went wrong? Should be 6/30 = 20%.

Hi CEdward

Actually, you wrote 36 boys failed the test whereas 40/100 of 80 boys is 32. This changed your overall result.
You get 32 boys who failed, 48 who passed and 16 girls who failed and 24 girls who passed.
24/120 = 4/20 = 20/100

Hope this helps
User avatar
glagad
Joined: 03 Jun 2022
Last visit: 30 Mar 2026
Posts: 329
Own Kudos:
Given Kudos: 116
Location: India
Concentration: Technology, Leadership
GMAT Focus 1: 645 Q90 V77 DI79
GPA: 8.98
GMAT Focus 1: 645 Q90 V77 DI79
Posts: 329
Kudos: 66
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I assumed the total number of B & G in the classroom quite late while solving the problem. While I got the correct answer, I got it after a long time.

My question -
a) Can we solve this question without assuming numbers? If yes, how?
b) How do we differentiate which questions can be easily solved using substitution (of values) over the algebraic methods/brute force approaches? Also, which questions should we not use the method of substitution?

Thanks
Moderators:
Math Expert
109809 posts
Tuck School Moderator
853 posts