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# A number is to be selected at random from the set above

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Manager
Joined: 16 Feb 2012
Posts: 216

Kudos [?]: 422 [2], given: 121

Concentration: Finance, Economics
A number is to be selected at random from the set above [#permalink]

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01 May 2012, 01:30
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Difficulty:

45% (medium)

Question Stats:

66% (00:46) correct 34% (00:51) wrong based on 273 sessions

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{-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10}

A number is to be selected at random from the set above. What is the probability that the number selected will be a solution of the equation (x-5)(x+10)(2x-5) = 0?

A. 1/12
B. 1/6
C. 1/4
D. 1/3
E. 1/2
[Reveal] Spoiler: OA

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Last edited by Bunuel on 01 May 2012, 01:41, edited 1 time in total.
Edited the question and added the OA

Kudos [?]: 422 [2], given: 121

Math Expert
Joined: 02 Sep 2009
Posts: 42578

Kudos [?]: 135427 [0], given: 12694

Re: A number is to be selected at random from the set above [#permalink]

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01 May 2012, 01:44
Expert's post
1
This post was
BOOKMARKED
Stiv wrote:
{-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10}

A number is to be selected at random from the set above. What is the probability that the number selected will be a solution of the equation (x-5)(x+10)(2x-5) = 0?

A. 1/12
B. 1/6
C. 1/4
D. 1/3
E. 1/2

Roots of the equation (x-5)(x+10)(2x-5)=0 are x=5, x=-10 and x=5/2=2.5. So, two solutions present in our set of 12 distinct numbers, therefore P=2/12=1/6.

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Kudos [?]: 135427 [0], given: 12694

Manager
Joined: 16 Feb 2012
Posts: 216

Kudos [?]: 422 [0], given: 121

Concentration: Finance, Economics
Re: A number is to be selected at random from the set above [#permalink]

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01 May 2012, 23:39
Aaaaaa OMG, I actually didn't notice that there isn't number 5(positive) in this bunch of numbers. I assumed it, and I got it wrong!

My advice to everyone: Don't assume anything!!!
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Kudos [?]: 422 [0], given: 121

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Re: A number is to be selected at random from the set above [#permalink]

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24 Jun 2016, 21:18
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: A number is to be selected at random from the set above [#permalink]

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20 Sep 2017, 20:14
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
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Kudos [?]: 287 [0], given: 0

Re: A number is to be selected at random from the set above   [#permalink] 20 Sep 2017, 20:14
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