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A, B, C and D are in Arithmetic Progression, what is the num

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A, B, C and D are in Arithmetic Progression, what is the num  [#permalink]

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New post 04 Aug 2019, 07:36
00:00
A
B
C
D
E

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  85% (hard)

Question Stats:

14% (01:24) correct 86% (02:00) wrong based on 29 sessions

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A, B, C and D are in Arithmetic Progression, what is the numerical value of ABCD?

1. B is equal to (A+C+D)/2
2. B is equal to A+2

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Joined: 19 Oct 2018
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Re: A, B, C and D are in Arithmetic Progression, what is the num  [#permalink]

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New post 04 Aug 2019, 16:48
Let the common difference is k
B= A+k, C=A+2k and D=A+3k

Statement 1- B=(A+C+D)/2
A+k=(A+A+2k+A+3k)/2
A+3k=0
D=0

Hence A*B*C*D=0
Sufficient

Statement 2-

Given- k=2
We can't find the value of A.

Insufficient







JayPatadiya wrote:
A, B, C and D are in Arithmetic Progression, what is the numerical value of ABCD?

1. B is equal to A+C+D/2
2. B is equal to A+2

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Joined: 24 Jun 2008
Posts: 1832
Re: A, B, C and D are in Arithmetic Progression, what is the num  [#permalink]

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New post 05 Aug 2019, 06:07
JayPatadiya wrote:
A, B, C and D are in Arithmetic Progression, what is the numerical value of ABCD?

1. B is equal to A+C+D/2
2. B is equal to A+2



The answer depends on whether there are missing brackets in Statement 1. If Statement 1 is supposed to read:

B = (A+C+D)/2

then the answer is A, because if A, B, C are equally spaced, B is always equal to (A+C)/2, so if it is also equal to (A+C+D)/2 = (A+C)/2 + D/2, then certainly D/2 = 0 and D = 0, so the product ABCD is 0. So Statement 1 is sufficient, and Statement 2 clearly is not, and the answer is A.

But if the bracketing is as written, the answer is C. If Statement 1 actually means

B = A + C + (D/2)

then if you replace A, B, C and D respectively with a, a + d, a + 2d and a + 3d, and solve, you'll end up finding that a = (-5/3)d. That's not sufficient, as any two examples will demonstrate. We'd need both Statements to answer the question (Statement 2 tells us d = 2, so we can use that to find a and thus find every term in the sequence, and thus answer any question about the sequence).
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Re: A, B, C and D are in Arithmetic Progression, what is the num  [#permalink]

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New post 05 Aug 2019, 06:11
This question is absolutely not GMAT-like. GMAC won't ask with such specific term "arithmetic progression".

Don't bother to entertain answering this question

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Re: A, B, C and D are in Arithmetic Progression, what is the num   [#permalink] 05 Aug 2019, 06:11
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