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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