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# Is x > 6? (1) x^2 = 49 (2) 7x = x^2

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Math Expert
Joined: 02 Sep 2009
Posts: 52921
Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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27 Feb 2018, 20:17
00:00

Difficulty:

25% (medium)

Question Stats:

68% (00:42) correct 32% (00:43) wrong based on 104 sessions

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Is x > 6?

(1) x^2 = 49
(2) 7x = x^2

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Posts: 1219
Location: India
GMAT 1: 730 Q49 V41
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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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27 Feb 2018, 20:48
Bunuel wrote:
Is x > 6?

(1) x^2 = 49
(2) 7x = x^2

Statement 1:
x=7 / -7 --Insufficient

Statement 2:
$$x^2$$ - 7x = 0
x(x-7) = 0
x=0 / 7 --Insufficient

Statement 1 & 2:
x=7 --Sufficient

IMO "C" is correct
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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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27 Feb 2018, 22:06
Statement 1:

X^2= 49
X= +7/-7
Insufficient

7X=X^2
X(X-7)=0
X= 0,7
Insufficient

Taking both the statement
X=7 sufficient
Ans: C

Correct me if I am wrong .

Sent from my Redmi Note 3 using GMAT Club Forum mobile app
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Joined: 05 Mar 2018
Posts: 2
Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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10 Mar 2018, 08:07
Hello,

Could we solve Statement #2 this way?
(2) 7x = x^2
7x = x*x
divide both sides by x to get
7=x
Is this correct? and if so, sufficient?
Math Expert
Joined: 02 Aug 2009
Posts: 7334
Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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10 Mar 2018, 08:13
1
francod9 wrote:
Hello,

Could we solve Statement #2 this way?
(2) 7x = x^2
7x = x*x
divide both sides by x to get
7=x
Is this correct? and if so, sufficient?

No you cannot..
You do not whether the variable 'x' is Positive or NEGATIVE..
If NEGATIVE, you can't divide by that variable..

Take it to one side $$7x=x^2…....x^2-7x=0......x(x-7)=0$$
So x can be 0 or 7
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html
4) Base while finding % increase and % decrease : https://gmatclub.com/forum/percentage-increase-decrease-what-should-be-the-denominator-287528.html

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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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10 Mar 2018, 08:25
chetan2u wrote:
francod9 wrote:
Hello,

Could we solve Statement #2 this way?
(2) 7x = x^2
7x = x*x
divide both sides by x to get
7=x
Is this correct? and if so, sufficient?

No you cannot..
You do not whether the variable 'x' is Positive or NEGATIVE..
If NEGATIVE, you can't divide by that variable..

Take it to one side $$7x=x^2…....x^2-7x=0......x(x-7)=0$$
So x can be 0 or 7

Thank you!
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Joined: 27 Oct 2017
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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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10 Mar 2018, 10:24
I don't agree with the below statement.
Since (2) 7x = x^2 is an equation, it doesn't matter whether x is negative or positive, we can divide by x on both sides of the equation
But yes we don't know that whether x is zero or non nero number, so we cannot divide by x.

,
chetan2u wrote:
francod9 wrote:
Hello,

Could we solve Statement #2 this way?
(2) 7x = x^2
7x = x*x
divide both sides by x to get
7=x
Is this correct? and if so, sufficient?

No you cannot..
You do not whether the variable 'x' is Positive or NEGATIVE..
If NEGATIVE, you can't divide by that variable..

Take it to one side $$7x=x^2…....x^2-7x=0......x(x-7)=0$$
So x can be 0 or 7

_________________
Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2   [#permalink] 10 Mar 2018, 10:24
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