Two probability questions in the second day of junior high school

1.(1+3+10+20)/500000 is not explained.

2. The probability is the same (according to the meaning of the question, don't put it back)

Consider grasping it in the order of a b c d e.

The probability of the first catch is 3/5.

B the probability of the second catch: P 1: A There are 2 places left (3/5)*(2/4).

P2: If A doesn't win, there are still 3 places (2/5)*(3/4).

P=P 1+P2=3/5

The probability of catching C for the third time: P 1: 1 position in A and B (3/5) * (2/4) * (1/3) =1/0.

P2: The number of unsuccessful places in A is (3/5)*(2/4)*(2/3)= 1/5.

P3: Miss A comes second, B (2/5)*(3/4)*(2/3)= 1/5.

P4: A missed B missed 3 digits (2/5) * (1/4) * (3/3) =110.

P=P 1+P2+P3+P4=3/5

Similarly, D E is more troublesome.

In short, the probability is 3/5.