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If (3 + a)(a/10 - 0.4) = -1, then a could be
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01 Mar 2021, 10:35
01 Mar 2021, 10:35
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If \((3 + a)(\frac{a}{10} - 0.4) = -1\), then a could be
A. -4
B. -2
C. 1
D. 2
E. 4
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
A. -4
B. -2
C. 1
D. 2
E. 4
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Re: If (3 + a)(a/10 - 0.4) = -1, then a could be
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01 Mar 2021, 12:01
01 Mar 2021, 12:01
Carcass wrote:
If \((3 + a)(\frac{a}{10} - 0.4) = -1\), then a could be
A. -4
B. -2
C. 1
D. 2
E. 4
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
A. -4
B. -2
C. 1
D. 2
E. 4
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
One approach is to eliminate the fractions/decimals first.
Given: (3 + a)(a/10 - 0.4) = -1
Multiply both sides by 10 to get: (3 + a)(a/10 - 0.4)(10) = (-1)(10)
Simplify: (3 + a)(a - 4) = -10
Expand and simplify: a² - a - 12 = -10
Add 10 to both sides: a² - a - 2 = 0
Factor: (a + 1)(a - 2) = 0
So, EITHER a = -1 OR a = 2
Answer: D
Alternatively, once you get to the point where you have the equation (3 + a)(a - 4) = -10, you could easily plug in the answer choices until you found the one that satisfies the equation (3 + a)(a - 4) = -10
Cheers,
Brent
gmatclubot
Re: If (3 + a)(a/10 - 0.4) = -1, then a could be [#permalink]
01 Mar 2021, 12:01
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