In a certain group of people, the average (arithmetic mean) : DS Archive
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# In a certain group of people, the average (arithmetic mean)

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SVP
Joined: 30 Mar 2006
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In a certain group of people, the average (arithmetic mean) [#permalink]

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17 Jun 2006, 10:12
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In a certain group of people, the average (arithmetic mean) weight of the males is 180 pounds and of the females, 120 pounds. What is the average weight of the people in the group?
(1) The group contains twice as many females as males.
(2) The group contains 10 more females than males.
Director
Joined: 06 May 2006
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17 Jun 2006, 11:22
A

#1. twice as many females

we get avg = [2k(120) + k(180)]/3k
k eliminated; sufficient

#2. 10 more females
unknown cannot be eliminated; insufficient
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VP
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17 Jun 2006, 11:27
1
KUDOS
A?
m = num of males
f = num of females
Avg = (180*m+120*f)/(m+f)

1. f = 2m
Avg = (180*m+120*2m)/(m+2m) = 420/3 = 140. SUFF
2. f = m+10
Avf = {180*m+120(m+10)}/(m+m+10) = (300m+1200)/(2m+10) INSUFF

Hence A.
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19 Jun 2006, 18:01
??? OA: A or D??? I got A too, but you said good work the answer is D?
VP
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19 Jun 2006, 22:30
A

19 Jun 2006, 22:30
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