If Sara's age is exactly twice Bill's age, what is Sara's ag : GMAT Data Sufficiency (DS)
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# If Sara's age is exactly twice Bill's age, what is Sara's ag

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If Sara's age is exactly twice Bill's age, what is Sara's ag [#permalink]

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18 Dec 2012, 06:43
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If Sara's age is exactly twice Bill's age, what is Sara's age?

(1) Four years ago, Sara's age was exactly 3 times Bill's age.
(2) Eight years from now, Sara's age will be exactly 1.5 times Bill's age.
[Reveal] Spoiler: OA
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Re: If Sara's age is exactly twice Bill's age, what is Sara's ag [#permalink]

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18 Dec 2012, 06:47
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If Sara's age is exactly twice Bill's age, what is Sara's age?

Given: S = 2B.

(1) Four years ago, Sara's age was exactly 3 times Bill's age --> S - 4 = 3(B-4). We have two distinct linear equations (S - 4 = 3(B-4) and S = 2B) with two unknowns, thus we can solve for both. Sufficient.

(2) Eight years from now, Sara's age will be exactly 1.5 times Bill's age --> S + 8 =1.5(B + 8). The same here: we have two distinct linear equations with two unknowns, thus we can solve for both. Sufficient.

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Re: If Sara's age is exactly twice Bill's age, what is Sara's ag [#permalink]

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19 Mar 2013, 13:00
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I solved this correctly via solving simultaneous equations ... but I could not understand the other approach the OG mentioned in the answer explanation : " another way to conclude that we can determine the value of s is to note that the pair of equations represents 2 non - parallel lines in the coordinate plane"
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Re: If Sara's age is exactly twice Bill's age, what is Sara's ag [#permalink]

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06 Apr 2013, 03:48
TheNona wrote:
I solved this correctly via solving simultaneous equations ... but I could not understand the other approach the OG mentioned in the answer explanation : " another way to conclude that we can determine the value of s is to note that the pair of equations represents 2 non - parallel lines in the coordinate plane"

What they try to say is that the equations can be considered linear functions with different slopes. Therefore they will intersect at a certain point leading to one solution.
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Re: If Sara's age is exactly twice Bill's age, what is Sara's ag [#permalink]

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10 Jan 2014, 09:31
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If Sara's age is exactly twice Bill's age, what is Sara's age?

(1) Four years ago, Sara's age was exactly 3 times Bill's age.
(2) Eight years from now, Sara's age will be exactly 1.5 times Bill's age.

We're given the equation S = 2B

1) S - 4 = 3(B - 4), we now have two equations and two unknowns, that's enough. Sufficient
2) S + 8 = 1.5(B + 8), again two equations and two unknowns, sufficient.

So, D.
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Re: If Sara's age is exactly twice Bill's age, what is Sara's ag [#permalink]

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12 Oct 2014, 00:59
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I thought the answer would be A because

2) S=2B
and S+8 = 1.5(B+8); solve this we have B=4/3.5 => B is not an integer => insufficient

Should B and S be integers because they are years of age?
Could someone help to explain when integers should be considered and when not?
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Re: If Sara's age is exactly twice Bill's age, what is Sara's ag [#permalink]

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12 Oct 2014, 01:21
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trambn wrote:
I thought the answer would be A because

2) S=2B
and S+8 = 1.5(B+8); solve this we have B=4/3.5 => B is not an integer => insufficient

Should B and S be integers because they are years of age?
Could someone help to explain when integers should be considered and when not?

When you solve S + 8 =1.5(B + 8) and S = 2B you get B = 8 and S = 16.

Also, why should a statement be insufficient if the result is not an integer?

And finally, I haven't seen a single official question where age is not an integer.

Check other Age Problems in our Speial Questions Directory.

Hope it helps
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Re: If Sara's age is exactly twice Bill's age, what is Sara's ag [#permalink]

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11 Sep 2015, 00:07
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we have 1 equation as per given data

Statement 1 : gives another equation along with Given data , can be solved , sufficient
Statement 2 : gives another equation along with Given data , can be solved , sufficient

hence D
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Re: If Sara's age is exactly twice Bill's age, what is Sara's ag [#permalink]

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28 Sep 2016, 17:11
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Re: If Sara's age is exactly twice Bill's age, what is Sara's ag   [#permalink] 28 Sep 2016, 17:11
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