Joshuautazi2021 wrote:
For every group of 10digit, there is one 2. Total of 10group = 10.
For every group of 10 digits, there is one 3, total of 10group = 10.
For number beginning with twenties, there are 10 but to avoid double counting we remove 1 = 9.
For numbers beginning with 3, there are also 9
Numbers that have 2 and 3 are 32 and 23.
P(2) + P(3) - P(2 and 3)
19 + 19 - 2 = 36
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