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 may not be repeated in an integer?
To form a two-digit integer, I need to choose one digit for the tens place and one digit for the units place. Since I cannot repeat digits, I have four choices for the tens place, and then three choices for the units place after I eliminate the one I already used. Therefore, the number of possible two-digit integers is 4 times 3, which is 12. 