How many strings of five decimal digits if Have exactly four digits that are 5s?

Question

Question

How many strings of five decimal digits if Have exactly four digits that are 5s?

math Statistics-And-Probability

Answer 1

Answer #1

there is only one digit which is different than 5 which can take any of the 5 positions

This one number can be selected from 0 to 9 except 5, this can be done in 9 ways

Hence number of strings = 5*9 = 45

Answer 2

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