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Re: If (3 + a)(a/10 - 0.4) = -1, then a could be [#permalink]

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03 Sep 2017, 07:57

Top Contributor

Bunuel wrote:

If \((3 + a)(\frac{a}{10} - 0.4) = -1\), then a could be

A. -4 B. -2 C. 1 D. 2 E. 4

Alternatively, once you get to the point where you have the equation (3 + a)(a - 4) = -10 [see my post above for how I got there], you could easily plug in the answer choices until you found the one that satisfies the equation (3 + a)(a - 4) = -10

Re: If (3 + a)(a/10 - 0.4) = -1, then a could be [#permalink]

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01 Oct 2017, 10:45

Bunuel wrote:

If \((3 + a)(\frac{a}{10} - 0.4) = -1\), then a could be

A. -4 B. -2 C. 1 D. 2 E. 4

Hi...

if I want to do it fast and use logic.. \(\frac{a}{10}-0.4=\frac{a-4}{10}\) so looking at the choices, 3+a should be a factor of 10... A) so a could be -4 as \(3-4=-1\) but then the RHS will become positive so discard B) a as -2 would make 3+a as 1 but \(\frac{a-4}{10}\) can never be -1 C) a as 1 gives 3+a as \(3+1=4\).. not a factor of 10.. Discard D) a as 2 gives 3+a as \(3+2 = 5\), a factor of 10.. try substituting .. FITs in E) a as 4 gives \(3+4=7\)... Discard

substitution this way would be way faster than finding solution of a
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