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just started. OG diag PS 14

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by ryantherocket » Tue Jul 13, 2010 6:44 am
Of the 84 parents who attended a meeting at a school, 35 volunteered to supervise children during the school picnic and 11 volunteered both to supervise children during the picnic and to bring refreshments to the picnic. If the number of parents who volunteered to bring refreshments was 1.5 times the number of parents who neither volunteered to supervise children during the picnic nor volunteered to bring refreshments, how many of the parents volunteered to bring refreshments?

A) 25
B) 36
C) 38
D) 42
E) 45

Please help. This one is overwhelming.
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by Rahul@gurome » Tue Jul 13, 2010 6:48 am
Please see the link https://www.beatthegmat.com/sets-problem-t58964.html
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by Patrick_GMATFix » Tue Jul 13, 2010 6:50 am
There are a couple of ways to solve this question. Group Formula and Venn Diagrams are two of them.

My preferred way would be to use the group formula, because we have 2 overlapping groups. Group 1 agreed to supervise and group 2 agreed to bring refreshments.

The group formula is Total = group1 + group2 + neither - both. Put in the data you have and solve for the number of ppl who agreed to bring refreshments. The answer is B

The OG Companion 12 solution is attached. This includes both of the methods discussed above in detail as well as a couple of take-away lessons for similar questions. Those who cannot view the attachment can read it here.

Hope that helps,
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by barcebal » Tue Jul 13, 2010 7:12 am
Patrick,

I like your formula of group1 + group2 +neither - both= total. I'm sure it's plastered in all the books, but I always write my formula

onlygroup1 + onlygroup2 + both + neither and then set up sub equations like

onlygroup1 + both = group1

Thanks for posting.
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by Patrick_GMATFix » Wed Jul 14, 2010 10:48 am
Barcebal, I like your formula too!
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