There are 9 Cards in a box, and there are numbers 1 to 9 on the cards. If two cards are randomly drawn out from the box, and the first card is drawn out, it needs to be put back into the box before the second card is drawn out, and the probability that the product of the extracted numbers is even is calculated There's a way I don't understand why it's not right. Please analyze it by an expert - one of the two must be even, and the other odd or even. Why can't we assume that (the probability of getting odd or even) is 1, and then set 1x4 / 9 (the probability of getting even) X2 (the order)?

There are 9 Cards in a box, and there are numbers 1 to 9 on the cards. If two cards are randomly drawn out from the box, and the first card is drawn out, it needs to be put back into the box before the second card is drawn out, and the probability that the product of the extracted numbers is even is calculated There's a way I don't understand why it's not right. Please analyze it by an expert - one of the two must be even, and the other odd or even. Why can't we assume that (the probability of getting odd or even) is 1, and then set 1x4 / 9 (the probability of getting even) X2 (the order)?

If you analyze in this way, you need to pay attention to the situation of repeated statistics: two times are even. This situation needs to be subtracted once