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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: 28
GMAT 1: 510 Q36 V26
GMAT 2: 550 Q38 V28
Followers: 0

Kudos [?]: 4 [0], given: 52

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

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18 Feb 2014, 01:32
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Difficulty:

15% (low)

Question Stats:

80% (01:41) correct 20% (01:13) wrong based on 115 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
[Reveal] Spoiler: OA

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Last edited by Bunuel on 29 Apr 2017, 03:15, 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: 38918
Followers: 7742

Kudos [?]: 106323 [2] , given: 11621

Re: For all numbers s and t, the operation * is defined by s*t [#permalink]

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18 Feb 2014, 01:47
2
KUDOS
Expert's post
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: 28
GMAT 1: 510 Q36 V26
GMAT 2: 550 Q38 V28
Followers: 0

Kudos [?]: 4 [0], given: 52

Re: For all numbers s and t, the operation * is defined by s*t [#permalink]

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18 Feb 2014, 02:23
Thanks Bunuel

Will keep the rules in mind.
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Please give me Kudos if you like my post. Thank you

Manager
Status: On a 600-long battle
Joined: 22 Apr 2016
Posts: 142
Location: Hungary
Schools: Erasmus '20
GMAT 1: 410 Q18 V27
GMAT 2: 490 Q35 V23
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Kudos [?]: 17 [1] , given: 392

Re: For all numbers s and t, the operation * is defined by s*t [#permalink]

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29 Apr 2017, 02:53
1
KUDOS
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: 38918
Followers: 7742

Kudos [?]: 106323 [0], given: 11621

Re: For all numbers s and t, the operation * is defined by s*t [#permalink]

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29 Apr 2017, 03:14
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   [#permalink] 29 Apr 2017, 03:14
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