The sets S1={15,9,20,7} and S2= {6,11,5,4} both have one or : Quant Question Archive [LOCKED]
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# The sets S1={15,9,20,7} and S2= {6,11,5,4} both have one or

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Intern
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The sets S1={15,9,20,7} and S2= {6,11,5,4} both have one or [#permalink]

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14 Oct 2007, 15:58
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

The sets S1={15,9,20,7} and S2= {6,11,5,4} both have one or more numbers over 10. If one number from S1 and one number from S2 are selected randomly, what is the probability that the set selected will have one number over 10 and one number under 10?

a) 3/16
b) 3/8
c) 7/16
d) 1/2
e) 5/8
Manager
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14 Oct 2007, 17:37
yes D

first case is where the num from S1 is over 10 and the number from S2 is under 10 => probability = 2/4 * 3/4 = 3/8

second case is where the num from S1 is under 10 and the num selected from S2 is over 10 => probability = 2/4 * 1/4 = 1/8

and you add these two cases up to get 3/8 + 1/8 = 1/2
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15 Oct 2007, 00:01
inwosu wrote:
The sets S1={15,9,20,7} and S2= {6,11,5,4} both have one or more numbers over 10. If one number from S1 and one number from S2 are selected randomly, what is the probability that the set selected will have one number over 10 and one number under 10?

a) 3/16
b) 3/8
c) 7/16
d) 1/2
e) 5/8

D.

1/2*3/4 = 3/8

1/2*1/4 = 1/8. 1-3/8-1/8 ---> 1/2
Director
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15 Oct 2007, 15:51
you can reword this problem

what's the probability that you get a number over 10 and one under == 100% - what's the probability that both numbers are under or over 10?

which is easy

1 - 3/8 - 1/8 = 1-4/8 = 1/2
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15 Oct 2007, 16:08
inwosu wrote:
The sets S1={15,9,20,7} and S2= {6,11,5,4} both have one or more numbers over 10. If one number from S1 and one number from S2 are selected randomly, what is the probability that the set selected will have one number over 10 and one number under 10?

a) 3/16
b) 3/8
c) 7/16
d) 1/2
e) 5/8

D

1/2 x 3/4 + 1/4 x 1/2=1/2
Re: Probability   [#permalink] 15 Oct 2007, 16:08
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