A, B, C are three consecutive positive integers (A>B>C

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A, B, C are three consecutive positive integers (A>B>C

by M7MBA » Mon Nov 06, 2017 6:37 am

A, B, C are three consecutive positive integers (A>B>C). What is the value of the expression 2A +B +3C?

A. 6A+7.
B. 5A+1.
C. 5A-1.
D. 6A-5.
E. 6A-7.

The OA is E.

What is the best approach to solve this PS question? Experts, can you help me?

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Source: Beat The GMAT — Problem Solving | Mon Nov 06, 2017 6:37 am

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by Brent@GMATPrepNow » Mon Nov 06, 2017 7:04 am

M7MBA wrote:A, B, C are three consecutive positive integers (A>B>C). What is the value of the expression 2A +B +3C?

A. 6A+7.
B. 5A+1.
C. 5A-1.
D. 6A-5.
E. 6A-7.

The OA is E.

What is the best approach to solve this PS question? Experts, can you help me?

Here's one approach:

Let the three consecutive positive integers be 1, 2 and 3
That is, A = 3, B = 2, C = 1

What is the value of the expression 2A +B +3C?
Well, if A = 3, B = 2, C = 1, then 2A +B +3C = 2(3) +2 +3(1) = 11

So, when A = 3, we find that A +B +3C = 11
Now test the answer choices, to see which one yields an output of 11, when A = 3

A. 6(3) + 7 = 25 ELIMINATE
B. 5(3) + 1 = 16 ELIMINATE
C. 5(3) - 1 = 14 ELIMINATE
D. 6(3) - 5 = 13 ELIMINATE
E. 6(3) - 7 = 11 KEEP

Answer: E

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Jeff@TargetTestPrep: GMAT Instructor; Posts: 1462; Joined: Thu Apr 09, 2015 9:34 am; Location: New York, NY; Thanked: 39 times; Followed by:22 members

by Jeff@TargetTestPrep » Mon Dec 18, 2017 4:43 pm

M7MBA wrote:A, B, C are three consecutive positive integers (A>B>C). What is the value of the expression 2A +B +3C?

A. 6A+7.
B. 5A+1.
C. 5A-1.
D. 6A-5.
E. 6A-7

Since the integers A, B, and C are consecutive integers (with A > B > C) and we see that the answer choices are in terms of A, we can say B = A - 1 and C = A - 2. Thus:

2A + B + 3C = 2A + A - 1 + 3(A - 2) = 3A - 1 + 3A - 6 = 6A - 7

Answer: E

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