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28 Dec 2017, 00:25
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E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
95% (01:16) correct
5%
(00:51)
wrong
based on 53
sessions
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The average of a, b, and c is 8, and the average of a and b is 10. If the average of a and c is 6, what is the value of a – c ?
A. 8
B. 7
C. 6
D. 5
E. 4
A. 8
B. 7
C. 6
D. 5
E. 4
28 Dec 2017, 04:13
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Bunuel
We'll start by writing by writing all our information as equations and then simplify them.
This is a Precise approach.
(a+b+c)/3 = 8 --> a+b+c=24
(a+b)/2 = 10 --> a+b=20
(a+c)/2 = 6 --> a+c=12
We'll subtract the first two equations to get c = 4
and substitute c=4 into our third equation to get a = 8
then a - c = 4
(E) is our answer.
28 Dec 2017, 05:36
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Bunuel
Substituting twice.
\(\frac{a + b + c}{3} = 8\)
\(a + b + c = 24\)
\(\frac{a + b}{2} = 10\)
\(a + b = 20\)
\(20 + c = 24\)
\(c = 4\)
\(\frac{a + c}{2} = 6\)
\(a + c = 12\)
\(c = 4\)
\(a = 8\)
\((a - c) = (8 - 4) = 4\)
Answer E
