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#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here. # If 12a + 3b = 1 and 7b – 2a = 9, what is the average (arithm  Question banks Downloads My Bookmarks Reviews Important topics
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TAGS: Moderator  Joined: 07 Jan 2018
Posts: 697
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Kudos [?]: 785  , given: 88

If 12a + 3b = 1 and 7b – 2a = 9, what is the average (arithm [#permalink]
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Question Stats: 75% (01:33) correct 25% (00:36) wrong based on 24 sessions
If 12a + 3b = 1 and 7b – 2a = 9, what is the average (arithmetic mean) of a and b ?

A) 0.1
B)0.5
C)1
D)2.5
E)5
[Reveal] Spoiler: OA GRE Instructor Joined: 10 Apr 2015
Posts: 3909
Followers: 164

Kudos [?]: 4777  , given: 70

Re: If 12a + 3b = 1 and 7b – 2a = 9, what is the average (arithm [#permalink]
2
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Expert's post
amorphous wrote:
If 12a + 3b = 1 and 7b – 2a = 9, what is the average (arithmetic mean) of a and b ?

A) 0.1
B)0.5
C)1
D)2.5
E)5

We COULD solve this system of equations for a and b, but this could take some time.
Also recognize that, to find the average of a and b, we need only find the SUM, a + b

GIVEN:
12a + 3b = 1
–2a + 7b = 9

ADD the two equations to get: 10a + 10b = 10
Divide both sides by 10 to get: a + b = 1

What is the average (arithmetic mean) of a and b?
Average = (a + b)/2 = 1/2 = 0.5

Cheers,
Brent
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Brent Hanneson – Creator of greenlighttestprep.com Intern Joined: 13 Jul 2018
Posts: 33
GRE 1: Q159 V151 GPA: 4
WE: Programming (Computer Software)
Followers: 0

Kudos [?]: 22 , given: 9

Re: If 12a + 3b = 1 and 7b – 2a = 9, what is the average (arithm [#permalink]
Taking the sum works the fastest here, as against substituting values. Re: If 12a + 3b = 1 and 7b – 2a = 9, what is the average (arithm   [#permalink] 17 Aug 2018, 16:05
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