How many 4-digit odd numbers can be formed from the digits 0, 1, 2, 3, 5, 7, 8, if the digits can be repeated?
There are 7 digits: "0,1,2,3,5,7,8."
There are 4 odd digits among these 7 digits: "1,3,5,7."
Then "7\\cdot7\\cdot7\\cdot4=1372" four-digit odd numbers can be formed from the digits 0, 1, 2, 3, 5, 7, 8, if the digits can be repeated.
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