+273 Given the four digits 2, 4, 6, and 7, how many different positive two-digit integers can be formed using these digits if a digit can be repeated in an integer?
+539 There are 4 possibilities for the first digit and 4 possibilities for the second. 4*4=16
+117 since all even numbers (2,4,6) will come is the last position, it can be filled in 3 ways, then the first place can be filled by 3 odd numbers + 2 even numbers (since one even number is fixed in the last position), the second position can be filled by 4 digits + 0 that is 5 digits, the third place can be filled by 4 digits and last place by 3,
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