Oct 20 07:00 AM PDT  09:00 AM PDT Get personalized insights on how to achieve your Target Quant Score. Oct 22 08:00 PM PDT  09:00 PM PDT On Demand for $79. For a score of 4951 (from current actual score of 40+) AllInOne Standard & 700+ Level Questions (150 questions) Oct 23 08:00 AM PDT  09:00 AM PDT Join an exclusive interview with the people behind the test. If you're taking the GMAT, this is a webinar you cannot afford to miss! Oct 26 07:00 AM PDT  09:00 AM PDT Want to score 90 percentile or higher on GMAT CR? Attend this free webinar to learn how to prethink assumptions and solve the most challenging questions in less than 2 minutes.
Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 58441

On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
30 Jun 2015, 05:05
Question Stats:
75% (01:08) correct 25% (01:33) wrong based on 239 sessions
HideShow timer Statistics
On a particular exam, the boys in a history class averaged 86 points and the girls in the class averaged 80 points. If the overall class average was 82 points, what was the ratio of boys to girls in the class? A. 1:4 B. 1:3 C. 1:2 D. 2:1 E. 3:1 Kudos for a correct solution.
Official Answer and Stats are available only to registered users. Register/ Login.
_________________



Manager
Joined: 20 Jul 2011
Posts: 79

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
30 Jun 2015, 10:03
Bunuel wrote: On a particular exam, the boys in a history class averaged 86 points and the girls in the class averaged 80 points. If the overall class average was 82 points, what was the ratio of boys to girls in the class?
A. 1:4 B. 1:3 C. 1:2 D. 2:1 E. 3:1
Kudos for a correct solution. Solution: We can use the X method to solve similar questions B...................G 86................80 ..........82........ 2..................4 Hence, Boys: Girls => 2: 4 => 1:2 Option C



Manager
Joined: 26 Dec 2011
Posts: 115

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
30 Jun 2015, 06:07
On a particular exam, the boys in a history class averaged 86 points and the girls in the class averaged 80 points. If the overall class average was 82 points, what was the ratio of boys to girls in the class? A. 1:4 B. 1:3 C. 1:2 D. 2:1 E. 3:1 Solution  Given that Boys average is 86 and Girls average is 80 points. Total average is 82 points. (86B+80G)/(B+G) = 82 > 4B=2G > B/G = 1/2. ANS C.
_________________



Retired Moderator
Status: On a mountain of skulls, in the castle of pain, I sit on a throne of blood.
Joined: 30 Jul 2013
Posts: 300

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
30 Jun 2015, 07:13
Bunuel wrote: On a particular exam, the boys in a history class averaged 86 points and the girls in the class averaged 80 points. If the overall class average was 82 points, what was the ratio of boys to girls in the class?
A. 1:4 B. 1:3 C. 1:2 D. 2:1 E. 3:1
Kudos for a correct solution. G B 80 86 82 4 2 2 : 1 G:B=2:1 B:G=1:2 Answer: C



Manager
Joined: 26 Dec 2012
Posts: 144
Location: United States
Concentration: Technology, Social Entrepreneurship
WE: Information Technology (Computer Software)

On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
Updated on: 30 Jun 2015, 11:20
Let # boys in the class=x & # of girls in class =y so we have (sum of boys)=86X (sum of girls)=80y
total average =82=> 86x+80y=82(x+y) =? we get 4x=2y so x/y =1/2
Hence answer is C Thanks,
Originally posted by lipsi18 on 30 Jun 2015, 10:30.
Last edited by lipsi18 on 30 Jun 2015, 11:20, edited 1 time in total.



Manager
Joined: 18 Mar 2014
Posts: 226
Location: India
Concentration: Operations, Strategy
GPA: 3.19
WE: Information Technology (Computer Software)

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
30 Jun 2015, 11:01
86  80 82 2 4 .... hence 2:4 = 1:2 Did cross subtraction here , 8682 = 4 , 8280 = 2 Required answer = 1:2 C
_________________
Press +1 Kudos if you find this Post helpful



Manager
Joined: 07 Apr 2015
Posts: 153

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
01 Jul 2015, 07:51
I think its 2:1 as question asks for the ratio of Boys to girls.
Let x be number of boys, y number of girls.
86x + 80y / (x+y) = 82
86x + 80y = 82x + 82y 4x = 2y 2x = y 2:1



Math Expert
Joined: 02 Sep 2009
Posts: 58441

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
06 Jul 2015, 02:59
Bunuel wrote: On a particular exam, the boys in a history class averaged 86 points and the girls in the class averaged 80 points. If the overall class average was 82 points, what was the ratio of boys to girls in the class?
A. 1:4 B. 1:3 C. 1:2 D. 2:1 E. 3:1
Kudos for a correct solution. MANHATTAN GMAT OFFICIAL SOLUTION:The boys in the class scored 4 points higher on average than the entire class. The boys have a + 4 differential. Similarly, the girls scored 2 points lower on average than the class. They have a  2 differential. You need to balance out the differentials: b*(+4) + g*(2) = 0 If b = 1 and g = 2, the equation will be true. Thus, the ratio of boys to girls is 1:2. Answer: C.
_________________



Senior Manager
Joined: 28 Jun 2015
Posts: 283
Concentration: Finance
GPA: 3.5

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
30 Jun 2015, 10:37
80  82  86 8682/8280 = 4/2 = 2/1. D.
_________________
I used to think the brain was the most important organ. Then I thought, look what’s telling me that.



Intern
Joined: 13 May 2015
Posts: 16
Concentration: Finance, General Management
GPA: 3.39

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
06 Oct 2016, 05:40
I got that 8682 & 8280 are the two sets of numbers we are using to arrive at the answer however im getting 2:1 and not 1:2..... help!



Current Student
Joined: 12 Aug 2015
Posts: 2567

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
10 Dec 2016, 10:26
Here is my solution for this one> Sum(Boys scores)=\(86*B\) Sum(Girls scores)=\(80*G\) Total > \(86*B+80*G = 82*B+82*G\) Hence \(4B=2G => \frac{B}{G}=\frac{1}{2}\)
Hence C
_________________



VP
Joined: 14 Feb 2017
Posts: 1200
Location: Australia
Concentration: Technology, Strategy
GMAT 1: 560 Q41 V26 GMAT 2: 550 Q43 V23 GMAT 3: 650 Q47 V33 GMAT 4: 650 Q44 V36
WE: Management Consulting (Consulting)

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
01 Aug 2017, 03:22
I can't seem to apply a consistent approach to weighted average problems. Could someone please point me to the right direction for a good explanation of the approach?
_________________
Goal: Q49, V41
+1 Kudos if I have helped you



Manager
Joined: 30 May 2012
Posts: 198
Location: United States (TX)
Concentration: Finance, Marketing
GPA: 3.3
WE: Information Technology (Consulting)

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
07 Aug 2017, 09:26
ashokk138 wrote: Bunuel wrote: On a particular exam, the boys in a history class averaged 86 points and the girls in the class averaged 80 points. If the overall class average was 82 points, what was the ratio of boys to girls in the class?
A. 1:4 B. 1:3 C. 1:2 D. 2:1 E. 3:1
Kudos for a correct solution. Solution: We can use the X method to solve similar questions B...................G 86................80 ..........82........ 2..................4 Hence, Boys: Girls => 2: 4 => 1:2 Option C I have come across this  "X  method" in several posts on this forum. Is there a theory/article describing this? Seems like a sure shot approach to weighted averages. Can someone point me to the resource, please?



Manager
Joined: 24 Jun 2017
Posts: 117

Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
Show Tags
07 Aug 2017, 12:22
lets x be the number of boys and y number of girls (86x + 80y) / (x + y) = 82 86x + 80 y = 82x + 82y 86x  82x = 82y  80y 4x = 2y 2x = y
1:2 (boys:girls)




Re: On a particular exam, the boys in a history class averaged 86 points a
[#permalink]
07 Aug 2017, 12:22






