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# For all numbers s and t, the operation * is defined by s*t

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Intern
Joined: 29 Jan 2014
Posts: 17
GMAT 1: 510 Q36 V26
GMAT 2: 550 Q38 V28
For all numbers s and t, the operation * is defined by s*t  [#permalink]

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Updated on: 29 Apr 2017, 02:15
00:00

Difficulty:

5% (low)

Question Stats:

82% (01:04) correct 18% (01:28) wrong based on 157 sessions

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For all numbers s and t, the operation * is defined by s*t = (s - 1)(t + 1). If (-2)*x = -12, then x =

(A) 2
(B) 3
(C) 5
(D) 6
(E) 11

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/for-all-numb ... 67915.html

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Originally posted by benjamin09 on 18 Feb 2014, 00:32.
Last edited by Bunuel on 29 Apr 2017, 02:15, edited 2 times in total.
Renamed the topic, edited the question, added the OA and moved to PS forum.
Math Expert
Joined: 02 Sep 2009
Posts: 52108
Re: For all numbers s and t, the operation * is defined by s*t  [#permalink]

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18 Feb 2014, 00:47
2
For all numbers s and t, the operation * is defined by s*t = (s - 1)(t + 1). If (-2)*x = -12, then x =

(A) 2
(B) 3
(C) 5
(D) 6
(E) 11

Since $$s*t = (s - 1)(t + 1)$$, then $$(-2)*x = (-2-1)(x+1)=-3(x+1)$$.

So, we are given that $$-3(x+1)=-12$$ --> $$x+1=4$$ -> $$x=3$$.

Hope it's clear.

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Intern
Joined: 29 Jan 2014
Posts: 17
GMAT 1: 510 Q36 V26
GMAT 2: 550 Q38 V28
Re: For all numbers s and t, the operation * is defined by s*t  [#permalink]

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18 Feb 2014, 01:23
Thanks Bunuel

Will keep the rules in mind.
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Manager
Status: On a 600-long battle
Joined: 21 Apr 2016
Posts: 137
Location: Hungary
Schools: Erasmus '19
GMAT 1: 410 Q18 V27
GMAT 2: 490 Q35 V23
Re: For all numbers s and t, the operation * is defined by s*t  [#permalink]

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29 Apr 2017, 01:53
1
This question has been discussed here: https://gmatclub.com/forum/for-all-numb ... 67915.html
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Math Expert
Joined: 02 Sep 2009
Posts: 52108
Re: For all numbers s and t, the operation * is defined by s*t  [#permalink]

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29 Apr 2017, 02:14
benjamin09 wrote:
For all numbers s and t, the operation * is defined by s*t = (s - 1)(t + 1). If (-2)*x = -12, then x =

(A) 2
(B) 3
(C) 5
(D) 6
(E) 11

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/for-all-numb ... 67915.html
_________________
Re: For all numbers s and t, the operation * is defined by s*t &nbs [#permalink] 29 Apr 2017, 02:14
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