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probability

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probability

by bacali » Tue Dec 02, 2008 9:56 am
Six cards numbered from 1 to 6 are placed in an empty bowl. First one card is drawn and then put back into the bowl; then a second card is drawn. If the cards are drawn at random and if the sum of the numbers on the cards is 8, what is the probability that one of the two cards drawn is
numbered 5 ?


A 1/6
B 1/5
C 1/3
D 2/5
E 2/3

OA: D
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Re: probability

by hwiya320 » Tue Dec 02, 2008 10:13 am
bacali wrote:Six cards numbered from 1 to 6 are placed in an empty bowl. First one card is drawn and then put back into the bowl; then a second card is drawn. If the cards are drawn at random and if the sum of the numbers on the cards is 8, what is the probability that one of the two cards drawn is
numbered 5 ?

D 2/5
correct me if I'm wrong.

It first states sum of two cards is 8
Possible outcome - card that will add upto 8 within 1-6 =
2,6
3,5
4,4
5,3
6,2
so 5 possible outcome. 5 only shows once, so you have 1/5 chance to pick 5 in the first draw.
Same for second draw, so 1/5 + 1/5 = 2/5
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