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A number is selected at random from the set above. what is the probabi

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A number is selected at random from the set above. what is the probabi [#permalink]

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New post 25 Oct 2010, 07:43
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{-10,-6,-5,-4,-2.5,-1,0,2.5,4,6,7,10}

A number is 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?

1/12
1/6
1/4
1/3
1/2
[Reveal] Spoiler: OA
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Re: A number is selected at random from the set above. what is the probabi [#permalink]

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New post 25 Oct 2010, 07:50
vanidhar wrote:
{-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10}

A number is selectedat random from the set above. what is the probablitiy that the number selected will be a solution of the equation (x-5)(x+10)(2x-5)=0?
1/12
1/6
1/4
1/3
1/2


Solutions of the equation \((x-5)(x+10)(2x-5)=0\) are: \(x=5\), \(x=-10\) and \(x=2.5\).

There are total of 12 numbers in the set {-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10} and it contains 2 roots: -10 and 2,5, so the probablitiy that the number selected will be a solution of the given equation is \(P=\frac{2}{12}=\frac{1}{6}\).

Answer: B.
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Re: A number is selected at random from the set above. what is the probabi [#permalink]

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New post 26 Oct 2010, 00:39
it contains 2 roots: -10 and 2.5 ??
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Re: A number is selected at random from the set above. what is the probabi [#permalink]

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New post 26 Oct 2010, 00:45
vanidhar wrote:
it contains 2 roots: -10 and 2.5 ??


Roots = Solution to the equation

We know the only solutions are -10,2.5,5
And of these, two are present in the set at hand
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Re: A number is selected at random from the set above. what is the probabi   [#permalink] 26 Oct 2010, 00:45
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