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On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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30 Jun 2015, 05:05
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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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.
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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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



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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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



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On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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.



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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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30 Jun 2015, 10:37
80  82  86 8682/8280 = 4/2 = 2/1. D.
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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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
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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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



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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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06 Jul 2015, 02:59



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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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!



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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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10 Dec 2016, 10:26



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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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?



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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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?



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Re: On a particular exam, the boys in a history class averaged 86 points a [#permalink]
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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)




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