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The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly

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The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly  [#permalink]

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New post 13 Jun 2017, 04:58
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Question Stats:

47% (02:23) correct 53% (02:40) wrong based on 115 sessions

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The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly 9 years older than Meghan. Natalie is how many years older than Meghan?

(1) In y years, Meghan will be exactly three times as old as Natalie is now.

(2) Lindsey is exactly 6 years older than Natalie.

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The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly  [#permalink]

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New post 13 Jun 2017, 05:22
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The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly 9 years older than Meghan. Natalie is how many years older than Meghan?

Let L: Lindsey's age, M:Meghan's age, N: Natalie's age.....All ages are in current time.

L + M = y.........1

L = M + 9.........2

From 1 in 2

2M + 9 = y.......3

N - M =????

(1) In y years, Meghan will be exactly three times as old as Natalie is now.

M + y = 3N.......4

From 3 in 4

M + 2M + 9 = 3N

3N - 3M = 9

N -M =3

Sufficient

(2) Lindsey is exactly 6 years older than Natalie.

L = N + 6......5

From 2 in 5

M + 9 = N + 6

N - M = 3

Sufficient

Answer: D
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Re: The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly  [#permalink]

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New post 13 Jun 2017, 09:38
From the question stem,
Let Meghan's age be M, Lindsey's age be L and Natalie's age is N.
Given data
L + M = y
L - M = 9 => L = M + 9 and M = L - 9
From this we can deduce(adding both equations)
2L = y+9 or y = 2L - 9

We need to find N-M to find out how much older is Natalie when compared to Meghan

1.From statement 1, we get M + y = 3N
M + 2L - 9 = 3N
Substituting value of L from the question stem,
M + 2(M+9) - 9 = 3N
3N - 3M =9 => N-M = 3. Hence sufficient

2.From statement 2, we get L - N = 6
M + 9 - N = 6(since L = M + 9)
N - M = 3. Hence, sufficient(Option d)
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The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly  [#permalink]

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New post 13 Jun 2017, 15:07
Another approach to the problem

The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly 9 years older than Meghan. Natalie is how many years older than Meghan?


Let L: Lindsey's age, M:Meghan's age, N: Natalie's age.....All ages are in current time.

Let M = 1 year

L = M + 9..........L = 10

y = L + M = 10 + 1 = 11

N - M =????

The question will be what is Natalie's age????

(1) In y years, Meghan will be exactly three times as old as Natalie is now.

M + y = 3N

1 +11 =3N..........N = 4

N -M =4 - 1 = 3

Sufficient

(2) Lindsey is exactly 6 years older than Natalie.

L = N + 6

10 = N +6

N= 4

N - M = 4 - 1= 3

Sufficient

Answer: D
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Re: The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly  [#permalink]

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New post 06 Jul 2017, 16:20
Bunuel wrote:
The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly 9 years older than Meghan. Natalie is how many years older than Meghan?

(1) In y years, Meghan will be exactly three times as old as Natalie is now.

(2) Lindsey is exactly 6 years older than Natalie.


We can let L = Lindsay’s current age, M = Meghan’s current age, and N = Natalie’s current age. Thus:

L + M = y

L = y - M

and

L = M + 9

Adding L = y - M and L = M + 9, we have:

2L = y + 9

y = 2L - 9

So, we now have the following equations:

L = y - M, L = M + 9, and y = 2L - 9.

We need to determine the value of N - M.

Statement One Alone:

In y years, Meghan will be exactly three times as old as Natalie is now.

Using the information in statement one, we can create the following equation:

M + y = 3N

Since y = 2L - 9, we have:

M + 2L - 9 = 3N

Since L = M + 9, we have:

M + 2(M + 9) - 9 = 3N

M + 2M + 18 - 9 = 3N

3M + 9 = 3N

3 = N - M

Statement one alone is sufficient to answer the question.

Statement Two Alone:

Lindsey is exactly 6 years older than Natalie.

We can create the following equation:

L = 6 + N

Since L = M + 9, we have:

M + 9 = 6 + N

N - M = 3

Statement two alone is sufficient to answer the question.

Answer: D
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Re: The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly  [#permalink]

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New post 06 Aug 2018, 07:36
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One thing I'd love to add to this one is a strategic note: if you look at the solutions here and in the Veritas Prep Practice Tests, the most common (and it's very common) mistake on this one is choosing B instead of D. So the mistake is "people don't realize that statement 1 is sufficient." And why not?

One of the easiest ways to trap people into picking a "less sufficient" answers is to ask for a combination of variables (instead of a specific variable itself). We're all really used to getting an equation and solving for x. But in most of our academic careers we rarely if ever solve directly for something like (2x - y) or, in this case, (N - M). For a lot of people, their natural inclination when they see:

Natalie is how many years older than Meghan?

Is to solve for Natalie's age, then solve for Meghan's age, then take the difference. But on Data Sufficiency, if the GMAT asks for a combination of variables (the difference between them, the sum of them, or something like that) it's almost always possible to solve for that combination with less information than it would take to solve for the variables individually, then combine. So when you see them ask for a combination, your instinct should be to "Leverage Assets" - really dig in to the algebra (as statement 1 requires here) to see if you can get directly to that combination. The fact that they asked that strange, overly-specific question is a clue that the right answer is probably "more sufficient" and the trap is "less sufficient," so perform your work accordingly.
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Re: The sum of the ages of Lindsey and Meghan is y, and Lindsey is exactly &nbs [#permalink] 06 Aug 2018, 07:36
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