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How many odd five-digit counting numbers can be formed by choosing digits from the set $\{1, 2, 3, 4, 5, 6, 7\}$ if digits can be repeated?

 Mar 28, 2020
 #1
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The place values can be anything, anything, odd

 

7*7*4=196 odd-five digit numbers.

 Mar 28, 2020
 #3
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1 -                7^4 x 4 =9604   Seven digits that can be repeated and which end in one of 4 odd digits [1, 3, 5, 7]

 

2 -                [7^5 x 4] /7 =9604  Five out of 7 digits that be can be repeated that can only end in [1, 3, 5, 7] out of 7.

 Mar 28, 2020
 #5
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7x7x7x7x4 as tertre said because only the last digits matters, as 1, 3, 5, and 7 are the odds of the group.

 Mar 28, 2020

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