GRE Prep 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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
On Monday, a class has 8 girls and 20 boys. On Tuesday, a ce
[#permalink]
17 Aug 2018, 17:12
17 Aug 2018, 17:12
Expert Reply
6
Bookmarks
00:00
Question Stats:
63% (02:11) correct
36% (02:34) wrong based on 72 sessions
Hide Show timer Statistics
On Monday, a class has 8 girls and 20 boys. On Tuesday, a certain number of girls joined the class just as twice that number of boys left the class, changing the ratio of girls to boys to 7 to 4. How many boys left the class on Tuesday?
(A) 5
(B) 6
(C) 11
(D) 12
(E) 18
(A) 5
(B) 6
(C) 11
(D) 12
(E) 18
Re: On Monday, a class has 8 girls and 20 boys. On Tuesday, a ce
[#permalink]
10 Jul 2019, 09:06
10 Jul 2019, 09:06
2
1
Bookmarks
sandy wrote:
On Monday, a class has 8 girls and 20 boys. On Tuesday, a certain number of girls joined the class just as twice that number of boys left the class, changing the ratio of girls to boys to 7 to 4. How many boys left the class on Tuesday?
(A) 5
(B) 6
(C) 11
(D) 12
(E) 18
(A) 5
(B) 6
(C) 11
(D) 12
(E) 18
This question can be solved in a number of different ways - including TESTing THE ANSWERS.
We know that there are 8 girls and 20 boys to start, and a certain number of girls joined and TWICE as many boys left the class (leaving us with a ratio of 7 girls for every 4 boys). We're asked for the number of boys that LEFT the class.
To start, since the number of boys who left is TWICE the number of girls who joined, the number of boys who left MUST be an EVEN number (so we can eliminate Answers A and C immediately).
Let's TEST Answer D: 12 boys
IF... 12 boys left and 6 girls joined, we would have....
8 + 6 = 14 girls
20 - 12 = 8 boys
14:8 = 7:4
This is an exact match for what we were told, so this MUST be the answer.
Final Answer: D
#CoPy.
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Re: On Monday, a class has 8 girls and 20 boys. On Tuesday, a ce
[#permalink]
10 Jul 2019, 09:47
10 Jul 2019, 09:47
2
1
Bookmarks
sandy wrote:
On Monday, a class has 8 girls and 20 boys. On Tuesday, a certain number of girls joined the class just as twice that number of boys left the class, changing the ratio of girls to boys to 7 to 4. How many boys left the class on Tuesday?
(A) 5
(B) 6
(C) 11
(D) 12
(E) 18
(A) 5
(B) 6
(C) 11
(D) 12
(E) 18
On Monday, a class has 8 girls and 20 boys. On Tuesday, a certain number of girls joined the class just as twice that number of boys left the class...
Let x = the number of GIRLS that JOINED the class
So, 2x = the number of BOYS that LEFT the class
So, 8 + x = the number of GIRLS in the class on TUESDAY (after the x girls joined)
And, 20 - 2x = the number of BOYS in the class on TUESDAY (after the 2x boys left)
...changing the ratio of girls to boys to 7 to 4
We can write: (8 + x)/(20 - 2x) = 7/4
Cross multiply to get: (4)(8 + x) = (7)(20 - 2x)
Expand: 32 + 4x = 140 - 14x
Subtract 32 from both sides: 4x = 108 - 14x
Add 14x to both sides: 18x = 108
Solve: x = 108/18 = 6
2x = the number of BOYS that LEFT the class.
So, 2(6) BOYS left the class
In other words, 12 BOYS left the class
Answer: D
Cheers,
Brent
