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If a + b = 9c, and 3a + 3b = 6d, then which of the following represent

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Joined: 02 Sep 2009
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If a + b = 9c, and 3a + 3b = 6d, then which of the following represent [#permalink]

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04 Jan 2018, 23:56
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If a + b = 9c, and 3a + 3b = 6d, then which of the following represents the average (arithmetic mean) of a, b, c, and d in terms of c?

A. 29c/8
B. 29c/6
C. 5c
D. 3c/2
E. 4c
[Reveal] Spoiler: OA

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Joined: 27 Dec 2017
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Re: If a + b = 9c, and 3a + 3b = 6d, then which of the following represent [#permalink]

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05 Jan 2018, 00:00
a+b= 9c; 3(a+b)=27c=6d: avg= (9c+4.5c+c) /4=29/8c

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If a + b = 9c, and 3a + 3b = 6d, then which of the following represent [#permalink]

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05 Jan 2018, 06:46
Bunuel wrote:
If a + b = 9c, and 3a + 3b = 6d, then which of the following represents the average (arithmetic mean) of a, b, c, and d in terms of c?

A. 29c/8
B. 29c/6
C. 5c
D. 3c/2
E. 4c

a+b = 9c => 3a+3b = 27c
Similarly, 3a+3b = 6d

Therefore, d = $$\frac{27c}{6} = \frac{9c}{2}$$

Average = $$\frac{a+b+c+d}{4} = (9c+c+\frac{9c}{2})*(\frac{1}{4}) = \frac{29c}{2}*\frac{1}{4} = \frac{29c}{8}$$(Option A)
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If a + b = 9c, and 3a + 3b = 6d, then which of the following represent   [#permalink] 05 Jan 2018, 06:46
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