ratios problem

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ratios problem

by alltimeacheiver » Fri Feb 11, 2011 12:06 am
In a certain English class, 1/4 of the number of girls is equal to 1/6 of the total number of
students. What is the ratio of the number of boys to the number of girls in the class?
A. 1 to 4
B. 1 to 3
C. 1 to 2
D. 2 to 3
E. 2 to 1
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by Night reader » Fri Feb 11, 2011 12:22 am
G/4=(G+B)/6, find B/G-?
6G=4G+4B, 2G=4B, 4B/2G=1, 2B/G=1, B/G=1/2
answer C
alltimeacheiver wrote:In a certain English class, 1/4 of the number of girls is equal to 1/6 of the total number of
students. What is the ratio of the number of boys to the number of girls in the class?
A. 1 to 4
B. 1 to 3
C. 1 to 2
D. 2 to 3
E. 2 to 1
Last edited by Night reader on Fri Feb 11, 2011 3:26 am, edited 1 time in total.

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by alltimeacheiver » Fri Feb 11, 2011 12:29 am
thank you...dear A ton thanks

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by alltimeacheiver » Fri Feb 11, 2011 12:38 am
thank you...dear A ton thanks

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by GMATGuruNY » Fri Feb 11, 2011 3:08 am
alltimeacheiver wrote:In a certain English class, 1/4 of the number of girls is equal to 1/6 of the total number of
students. What is the ratio of the number of boys to the number of girls in the class?
A. 1 to 4
B. 1 to 3
C. 1 to 2
D. 2 to 3
E. 2 to 1
Plug in girls = 4.
1/4 of the number of girls = 1/4 * 4 = 1.
Thus, there are 6 students total (since 1 = 1/6 * 6).
Boys = 6-4 = 2.
Boys:Girls = 2:4 = 1:2.

The correct answer is C.
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by gmatstudent2017 » Sun Sep 03, 2017 7:30 am
Hi GMATGuru,

I attempted to solve this problem by picking numbers as well; however, I picked a number for the total number of students instead of for the number of girls. I thought you would have to pick a number for the total and then use that to figure out how many girls there are and then subtract that amount from the total to get the number of boys. However, when I did that the ratio I ended up getting for boys to girls wasn't even an answer choice. For example, I picked the total to be 24 since that is a multiple of both 4 and 6. 1/6 of 24 is 4 and 24 - 4 is 20 so the ratio I got was 5:1. My question is, why do you pick a number for the girls and not for the total number of students?

Thank you.

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by Brent@GMATPrepNow » Sun Sep 03, 2017 7:45 am
gmatstudent2017 wrote:Hi GMATGuru,

I attempted to solve this problem by picking numbers as well; however, I picked a number for the total number of students instead of for the number of girls. I thought you would have to pick a number for the total and then use that to figure out how many girls there are and then subtract that amount from the total to get the number of boys. However, when I did that the ratio I ended up getting for boys to girls wasn't even an answer choice. For example, I picked the total to be 24 since that is a multiple of both 4 and 6. 1/6 of 24 is 4 and 24 - 4 is 20 so the ratio I got was 5:1. My question is, why do you pick a number for the girls and not for the total number of students?

Thank you.
You can pick a number for the TOTAL number of students. You just need to be careful.
Say there's a TOTAL of 24 students
1/4 of the number of girls is equal to 1/6 of the total number of students
1/6 of 24 = 4
This means 1/4 of the number of girls is equal to 4
In other words, there are 16 girls (since 1/4 of 16 = 4)
If 16 of the 24 students are girls, then the remaining 8 students are boys

So, BOYS:GIRLS = 8:16 = 1:2 = C
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by gmatstudent2017 » Sun Sep 03, 2017 9:42 am
Ahh, I see my mistake. Thank you so much for the explanation and clarification, Brent!
Brent@GMATPrepNow wrote:
gmatstudent2017 wrote:Hi GMATGuru,

I attempted to solve this problem by picking numbers as well; however, I picked a number for the total number of students instead of for the number of girls. I thought you would have to pick a number for the total and then use that to figure out how many girls there are and then subtract that amount from the total to get the number of boys. However, when I did that the ratio I ended up getting for boys to girls wasn't even an answer choice. For example, I picked the total to be 24 since that is a multiple of both 4 and 6. 1/6 of 24 is 4 and 24 - 4 is 20 so the ratio I got was 5:1. My question is, why do you pick a number for the girls and not for the total number of students?

Thank you.
You can pick a number for the TOTAL number of students. You just need to be careful.
Say there's a TOTAL of 24 students
1/4 of the number of girls is equal to 1/6 of the total number of students
1/6 of 24 = 4
This means 1/4 of the number of girls is equal to 4
In other words, there are 16 girls (since 1/4 of 16 = 4)
If 16 of the 24 students are girls, then the remaining 8 students are boys

So, BOYS:GIRLS = 8:16 = 1:2 = C