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GRE Prep Club Team Member
Joined: 20 Feb 2017
Posts: 2506
Given Kudos: 1053
GPA: 3.39
If −4 < a < 4 and −2 < b < −1, which of the following could NOT be the
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31 Jan 2021, 05:17
31 Jan 2021, 05:17
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Question Stats:
69% (01:40) correct
30% (01:57) wrong based on 59 sessions
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If −4 < a < 4 and −2 < b < −1, which of the following could NOT be the value of ab?
(A) −3
(B) 0
(C) 4
(D) 6
(E) 9
(A) −3
(B) 0
(C) 4
(D) 6
(E) 9
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
If 4 < a < 4 and 2 < b < 1, which of the following could NOT be the
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31 Jan 2021, 05:33
31 Jan 2021, 05:33
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GeminiHeat wrote:
If −4 < a < 4 and −2 < b < −1, which of the following could NOT be the value of ab?
(A) −3
(B) 0
(C) 4
(D) 6
(E) 9
(A) −3
(B) 0
(C) 4
(D) 6
(E) 9
APPROACH #1: Determine maximum and minimum values
If it were the case that −4 ≤ a ≤ 4 and −2 ≤ b ≤ −1, then...
- the value of ab is MINIMIZED when a = 4 and b = -2, to get -8
- the value of ab is MAXIMIZED when a = -4 and b = -2, to get 8
So, we can conclude that -8 < ab < 8, in which case we can see that answer choice E (9) is the only value that's OUTSIDE the range of possible values of ab
Answer: E
APPROACH #2: Process of elimination
If a = 2 and b = -1.5. then ab = -3. Eliminate A.
If a = 0 and b = -1.5. then ab = 0. Eliminate B.
If a = -3 and b = -4/3. then ab = 4. Eliminate C.
If a = -7/2 and b = -12/7. then ab = 6. Eliminate D.
By the process of elimination, the correct answer is E
Re: If −4 < a < 4 and −2 < b < −1, which of the following could NOT be the
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02 Feb 2021, 05:55
02 Feb 2021, 05:55
In this type of questions, always go for the Max and/or Min. Just by looking at the answer choices, we can see the choice E is more than the maximum product of the a and b : 9 > -3.99 x -1.99. Hence, the answer is E.
