Let S be the set of all positive four digit integers. For each of the following questions, you first give your answer that reflects your recipe, then simplify your answer to a number and give your explanation which includes your recipe(s). (a) How may numbers in S have at least one digit that is a 2 or a 5? (b) How may numbers in S have at least one digit that is a 2 and at least one digit that is a 5? (c) How may numbers in S have the property that the sum of its digits is even? (d) How may numbers in S have the property that its digits appear in the decreasing order (that is, the first digit is larger than the second digit, the second digit is larger than the third digit, and the third digit is larger than the last digit)?
Let S be the set of all positive four digit integers. For each of the following questions, you first give your answer
that reflects your recipe, then simplify your answer to a number and give your explanation which includes your recipe(s).
(a) How may numbers in S have at least one digit that is a 2 or a 5?
(b) How may numbers in S have at least one digit that is a 2 and at least one digit that is a 5?
(c) How may numbers in S have the property that the sum of its digits is even?
(d) How may numbers in S have the property that its digits appear in the decreasing order (that is, the first digit is
larger than the second digit, the second digit is larger than the third digit, and the third digit is larger than the last digit)?
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