00:01
We want to compute the probability that the drawn card is an eighth.
00:06
So we classify the situation into two cases.
00:11
In case one, the interchange card is selected.
00:16
And in case two, the interchangeer card is not selected.
00:22
And then there are three subcases.
00:26
In a subcase one, the second half deck has one one eighth.
00:48
So this drawing is another egg.
00:57
In the second set case, there are two is in the second half deck.
01:04
And in the third case, there are three ace in the second half deck.
01:10
Know that it's impossible to have four eighths in the second half deck, since we know that one is drawn from the first half deck.
01:20
And also, it's impossible to have four eights in the second half deck.
01:22
And also, it's impossible to be zero in case two.
01:26
Otherwise, we can't draw another eighth.
01:31
So now, now's compute all these probabilities.
01:36
The probability of the first case is 1 over 27, since now there are 27 cards in the second half deck, and the interchangeer card is drawn.
01:54
For the second case, the probability, the it is 26 over 27...