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Is xy< 10? 1) x<2 2) y<5

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Is xy< 10? 1) x<2 2) y<5 [#permalink]

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New post 24 Sep 2017, 23:47
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A
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E

Difficulty:

  5% (low)

Question Stats:

79% (00:26) correct 21% (00:20) wrong based on 76 sessions

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[GMAT math practice question]

Is xy< 10?

1) x<2
2) y<5
[Reveal] Spoiler: OA

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Re: Is xy< 10? 1) x<2 2) y<5 [#permalink]

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New post 24 Sep 2017, 23:56
MathRevolution wrote:
[GMAT math practice question]

Is xy< 10?

1) x<2
2) y<5


(1) We dont know value of y. Insufficient.

(2) We dont know value of x. Insufficient.

Combine (1) and (2).

If x and y are positive, then xy < 2 * 5 = 10.

If x and y are negative, for example, x = -2 and y = -10, then xy= (-2) * (-10) = 20 > 10.

Insufficient.

Answer is E.
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Re: Is xy< 10? 1) x<2 2) y<5 [#permalink]

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New post 24 Sep 2017, 23:58
1. x is less than 2 so x can be positive (<2 of course), 0 or negative. But since we don't know the value of y we cannot comment on the value of xy
so Insufficient

2. y is less than 5 so y can be positive (<5 of course), 0 or negative. But since we don't know the value of x we cannot comment on the value of xy
so insufficient

1 & 2 we know know that x< 2 and y<5 but still this information is inconclusive for eg x= 1 and y =4 then xy =4 and the question stem is true
if x = -2 and y = -5 then xy = 10 so question stem becomes false.
Hence both the statements together are also insufficient

answer is (e)

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Re: Is xy< 10? 1) x<2 2) y<5 [#permalink]

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New post 25 Sep 2017, 07:07
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MathRevolution wrote:

Is xy < 10?

1) x < 2
2) y < 5


Target question: Is xy< 10?

Statement 1: x < 2
Since there's no information about y, this statement is not sufficient.
However, if we're not certain about this insufficiency, we can TEST some values.
There are several values of x and y that satisfy statement 1. Here are two:
Case a: x = 1 and y = 1, which means xy = (1)(1) = 1. So, xy < 10
Case b: x = 1 and y = 20, which means xy = (1)(20) = 1. So, xy > 10
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: y < 5
Since there's no information about x, this statement is not sufficient.
Let's test some values (for "fun")
Case a: x = 1 and y = 1, which means xy = (1)(1) = 1. So, xy < 10
Case b: x = 10 and y = 2, which means xy = (10)(2) = 20. So, xy > 10
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
There are still several values of x and y that satisfy BOTH statements and yield contradictory answers to the target question. Here are two:
Case a: x = 1 and y = 1, which means xy = (1)(1) = 1. So, xy < 10
Case b: x = -5 and y = -6, which means xy = (-5)(-6) = 30. So, xy > 10
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer:
[Reveal] Spoiler:
E


Cheers,
Brent
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Re: Is xy< 10? 1) x<2 2) y<5 [#permalink]

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New post 25 Sep 2017, 12:22
Hey brent please reply to mine ques also

Sent from my ASUS_Z010D using GMAT Club Forum mobile app

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Re: Is xy< 10? 1) x<2 2) y<5 [#permalink]

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New post 25 Sep 2017, 12:33
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amanred wrote:
Hey brent please reply to mine ques also

Sent from my ASUS_Z010D using GMAT Club Forum mobile app


Where's your question?

Cheers,
Brent
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Re: Is xy< 10? 1) x<2 2) y<5 [#permalink]

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New post 27 Sep 2017, 00:35
=>

Condition 1) & 2)
x = 1, y = 2 ➔ xy = 2 < 10 : Yes
x = -3, y = -4 ➔ xy = 12 > 10 : No
Both conditions together are not sufficient.

Ans: E
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Re: Is xy< 10? 1) x<2 2) y<5   [#permalink] 27 Sep 2017, 00:35
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