ratios problem

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alltimeacheiver: Master | Next Rank: 500 Posts; Posts: 183; Joined: Wed Feb 09, 2011 3:08 amFollowed by: 5 members; Location: Delhi; Thanked: 1 times

by alltimeacheiver » Fri Feb 11, 2011 12:06 am

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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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Source: Beat The GMAT — Problem Solving | Fri Feb 11, 2011 12:06 am

Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

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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alltimeacheiver: Master | Next Rank: 500 Posts; Posts: 183; Joined: Wed Feb 09, 2011 3:08 amFollowed by: 5 members; Location: Delhi; Thanked: 1 times

by alltimeacheiver » Fri Feb 11, 2011 12:29 am

thank you...dear A ton thanks

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alltimeacheiver: Master | Next Rank: 500 Posts; Posts: 183; Joined: Wed Feb 09, 2011 3:08 amFollowed by: 5 members; Location: Delhi; Thanked: 1 times

by alltimeacheiver » Fri Feb 11, 2011 12:38 am

thank you...dear A ton thanks

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

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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gmatstudent2017: Newbie | Next Rank: 10 Posts; Posts: 7; Joined: Tue Aug 22, 2017 3:16 pm

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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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

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

Brent Hanneson - Creator of GMATPrepNow.com

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gmatstudent2017: Newbie | Next Rank: 10 Posts; Posts: 7; Joined: Tue Aug 22, 2017 3:16 pm

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

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