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# There are 6 cards numbered from 1 to 6. They are placed into

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Manager
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There are 6 cards numbered from 1 to 6. They are placed into [#permalink]  16 Oct 2008, 19:37
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
1/3

*As both event are mutual exclusive , we must consider 4,4 as two times instead of 1times.

else there wont be 36 (6*6) combination at all.. we will end up with 35 combination.

Please elabarote it. A similar theread is there but it does not discuss this point.

Thanks
Current Student
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Re: why not 36 [#permalink]  16 Oct 2008, 21:05
if the sum is 8, then possibilities are either 2 and 6 or 5 and 3..so what is the probability that we will have a 5?
well i get 1 - (probability its 2 or 6)/..1- (1/4+1/4) i.e 1/2
VP
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Re: why not 36 [#permalink]  16 Oct 2008, 21:07
vishalgc 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
1/3

*As both event are mutual exclusive , we must consider 4,4 as two times instead of 1times.

else there wont be 36 (6*6) combination at all.. we will end up with 35 combination.

Please elabarote it. A similar theread is there but it does not discuss this point.

Thanks

Here we are having only 6 cards to start with. After we pick out the card we "replace" it.

Say we pick out 4 the first time. We keep the card back. Now we pick out another card, there is only one 4 in the pack of six. So we can pick out only one 4.

There is only one (4,4) possibility.
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Re: why not 36 [#permalink]  16 Oct 2008, 22:34
there are only 5 scenarios where the sum will be 8 - 2,6 6,2 3,5 5,3 4,4
what is the OA??
Manager
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Re: why not 36 [#permalink]  17 Oct 2008, 02:56
tharunv wrote:
there are only 5 scenarios where the sum will be 8 - 2,6 6,2 3,5 5,3 4,4
what is the OA??

eggjacktly
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Re: why not 36 [#permalink]  17 Oct 2008, 05:16
i am getting 1/3

there are total three possibilities (2,6) (3,5) (4,4)

so probability of getting a 5 is 1/3

what is the OA
Re: why not 36   [#permalink] 17 Oct 2008, 05:16
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