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# If b=8d - c, and a=d/3, what is the average of a,b,c and d?

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VP
Joined: 31 Oct 2013
Posts: 1464
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
If b=8d - c, and a=d/3, what is the average of a,b,c and d?  [#permalink]

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01 Mar 2019, 10:05
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25% (medium)

Question Stats:

78% (01:49) correct 22% (02:09) wrong based on 36 sessions

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If b=8d - c, and a=d/3, what is the average of a,b,c and d?

A) 4a
B) 7a
C) a/7
D) 4a + 7
E) a/7 + 5
Manager
Joined: 19 Jan 2019
Posts: 88
Re: If b=8d - c, and a=d/3, what is the average of a,b,c and d?  [#permalink]

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01 Mar 2019, 10:50
1
Assume the value of a to be 4.
4 = d/3 => d = 12
b = 8d - c => b = 96-c
b+c = 96
Average of a,b,c,d = (a+b+c+d)/4
(4+12+96)/4 = 28..

Substitute the value of a as 4 in answer choices, we get option b as 28..

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Senior Manager
Joined: 15 Feb 2018
Posts: 365
Re: If b=8d - c, and a=d/3, what is the average of a,b,c and d?  [#permalink]

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01 Mar 2019, 20:42
Have each letter in terms of d
a=d/3
b=8d-c, b+c=8d
d=d

$$\frac{\frac{d}{3}+8d+d}{4}=\frac{\frac{28d}{3}}{4}=\frac{7d}{3}$$
The options are in terms of a, and we are told that a=d/3

$$\frac{7d}{3}=7a$$

B
Intern
Joined: 27 Nov 2018
Posts: 36
GMAT 1: 510 Q33 V28
Re: If b=8d - c, and a=d/3, what is the average of a,b,c and d?  [#permalink]

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26 May 2019, 09:51
1
philipssonicare wrote:
Have each letter in terms of d
a=d/3
b=8d-c, b+c=8d
d=d

$$\frac{\frac{d}{3}+8d+d}{4}=\frac{\frac{28d}{3}}{4}=\frac{7d}{3}$$
The options are in terms of a, and we are told that a=d/3

$$\frac{7d}{3}=7a$$

B

Since answer is in multiples of a , it is better to convert each letter in terms of "a". No need to convert c in any form as it will get cancelled out while we write the average formula
d= 3a
b= 8d-c = 24a-c

(a+b+c+d)/4 = (a+24a-c+c+3a)/4 = 28a/4 = 7a
Re: If b=8d - c, and a=d/3, what is the average of a,b,c and d?   [#permalink] 26 May 2019, 09:51
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