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GMAT Prep Probability

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GMAT Prep Probability

by naveenhv » Fri May 06, 2011 9:23 am
{-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 will be a solution to the equation (x-5)(x+10)(2X+5) = 0?

a) 1/12

b) 1/6

c) 1/4

d) 1/3

e) 1/2
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by manpsingh87 » Fri May 06, 2011 9:59 am
naveenhv 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 will be a solution to the equation (x-5)(x+10)(2X+5) = 0?

a) 1/12

b) 1/6

c) 1/4

d) 1/3

e) 1/2
out of 12 nos. any one no. can be selected in 12C1 ways=12;
now (x-5)(x+10)(2X+5) = 0; will become zero if x=5;x=-10 or x=-2.5;

therefore required probability is 3/12=1/4 hence C
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by clock60 » Fri May 06, 2011 10:18 am
i agree with above poster in a whole with one small correction
in the list of numbers we have no integer x=5, but rather x=2,5.
so resulted prob=2/12=1/6
and answer is B
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by manpsingh87 » Fri May 06, 2011 10:19 am
clock60 wrote:i agree with above poster in a whole with one small correction
in the list of numbers we have no integer x=5, but rather x=2,5.
so resulted prob=2/12=1/6
and answer is B
yep... clock60 thanks for the correction....!!! answer indeed in 1/6;
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