From a group of boys and girls, 15 girls leave. There are then let two boys for each girl. After this 45 boys leave. There are then 5 girls for each boy. The number of girls in the beginning was?
A. 29
B. 40
C. 43
D. 48
E. None of these
The OA is B.
Please, can any expert explain this PS question for me? I tried to solve it but I can't get the correct answer. I need your help. Thanks.
From a group of boys and girls, 15 girls leave...
This topic has expert replies
GMAT/MBA Expert
- Jay@ManhattanReview
- GMAT Instructor
- Posts: 3008
- Joined: Mon Aug 22, 2016 6:19 am
- Location: Grand Central / New York
- Thanked: 470 times
- Followed by:34 members
Say there were x girls.swerve wrote:From a group of boys and girls, 15 girls leave. There are then left two boys for each girl. After this 45 boys leave. There are then 5 girls for each boy. The number of girls in the beginning was?
A. 29
B. 40
C. 43
D. 48
E. None of these
The OA is B.
Please, can any expert explain this PS question for me? I tried to solve it but I can't get the correct answer. I need your help. Thanks.
After the 15 gilrs left, the number of girls left = (x - 15)
=> the number of boys now = 2(x - 15) = 2x - 30; it is given that there are then left two boys for each girl
After 45 boys left, the number of boys left = 2x - 30 - 45 = 2x - 75
=> the number of girls now = 5(2x - 75) = 10x - 375; it is given that there are then 5 girls for each boy
10x - 375 must be equal to x - 15
Thus, 10x - 375 = x - 15
=> x = 40
The correct answer: B
Hope this helps!
-Jay
_________________
Manhattan Review GMAT Prep
Locations: New York | Singapore | London | Dubai | and many more...
Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
GMAT/MBA Expert
- Scott@TargetTestPrep
- GMAT Instructor
- Posts: 7242
- Joined: Sat Apr 25, 2015 10:56 am
- Location: Los Angeles, CA
- Thanked: 43 times
- Followed by:29 members
We can let b = number of boys and g = number of girls originally in the group. Thus, we have:swerve wrote:From a group of boys and girls, 15 girls leave. There are then let two boys for each girl. After this 45 boys leave. There are then 5 girls for each boy. The number of girls in the beginning was?
A. 29
B. 40
C. 43
D. 48
E. None of these
b/(g - 15) = 2/1
and
(b - 45)/(g - 15) = 1/5
Simplifying the first equation, we have:
b = 2(g - 15)
b = 2g - 30
Substituting this into the second equation, we have:
(2g - 30 - 45)/(g - 15) = 1/5
5(2g - 75) = g - 15
10g - 375 = g - 15
9g = 360
g = 40
Answer: B
Scott Woodbury-Stewart
Founder and CEO
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews