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There are 6 cards numbered from 1 to 6. They are placed into [#permalink]
 09 Sep 2008, 05:46
There are 6 cards numbered from 1 to 6. They are placed into a box, and then one is drawn and put back and then another card is drawn and put back. What is the probability that one of the cards was 5 if the sum of the two was 8?
1
2/3
1/2
2/5
1/5
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Re: card probability [#permalink]
09 Sep 2008, 05:56
Probability gives me headache....trying.
The first card could be a 5 or 3. The second card needs to be either 3 or 5 respectively.
Thus, probability of first card being 5 and second card being 3 = 1/6 + 1/6 = 1/3
Similarly, probability of first card being 3 and second card being 5 = 1/6 + 1/6 = 1/3
Combining both, it should be 1/3 + 1/3 = 2/3.
Probability gurus, please comment.
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Re: card probability [#permalink]
09 Sep 2008, 06:40
arjtryarjtry wrote: There are 6 cards numbered from 1 to 6. They are placed into a box, and then one is drawn and put back and then another card is drawn and put back. What is the probability that one of the cards was 5 if the sum of the two was 8?
1
2/3
1/2
2/5
1/5 possible combinations: 3,55,32,6 6,2 4,4 probability= 2/5
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Re: card probability [#permalink]
09 Sep 2008, 08:15
i thought the ans should be 1/6*1/6 + 1/6*1/6.
there are totally 6 ways of picking up the cards right?
thats what is the definiton of possible cases. its possible to pick up any of the 6 cards right?
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Re: card probability [#permalink]
09 Sep 2008, 08:31
arjtryarjtry wrote: i thought the ans should be 1/6*1/6 + 1/6*1/6.
there are totally 6 ways of picking up the cards right?
thats what is the definiton of possible cases. its possible to pick up any of the 6 cards right? Read the question again.. and ...again What is the probability that one of the cards was 5 if the sum of the two was 8?
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Re: card probability [#permalink]
09 Sep 2008, 10:24
x2suresh wrote: arjtryarjtry wrote: There are 6 cards numbered from 1 to 6. They are placed into a box, and then one is drawn and put back and then another card is drawn and put back. What is the probability that one of the cards was 5 if the sum of the two was 8?
1
2/3
1/2
2/5
1/5 possible combinations: 3,55,32,6 6,2 4,4 probability= 2/5 Thanks x2suresh. I wish I could think probability problems in these simple terms....not sure why I have got fobia to probability.
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Current Student
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Re: card probability [#permalink]
09 Sep 2008, 10:26
x2suresh wrote: arjtryarjtry wrote: i thought the ans should be 1/6*1/6 + 1/6*1/6.
there are totally 6 ways of picking up the cards right?
thats what is the definiton of possible cases. its possible to pick up any of the 6 cards right? Read the question again.. and ...again What is the probability that one of the cards was 5 if the sum of the two was 8?hmm.. i still think that the problem is not well worded...
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Re: card probability [#permalink]
09 Sep 2008, 11:43
arjtryarjtry wrote: x2suresh wrote: arjtryarjtry wrote: i thought the ans should be 1/6*1/6 + 1/6*1/6.
there are totally 6 ways of picking up the cards right?
thats what is the definiton of possible cases. its possible to pick up any of the 6 cards right? Read the question again.. and ...again What is the probability that one of the cards was 5 if the sum of the two was 8?hmm.. i still think that the problem is not well worded... I found no ambiguity in the question. ans is clearly 2/5
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Re: card probability
[#permalink]
09 Sep 2008, 11:43
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