To identify all the factors of 81, we need to find all the whole numbers that divide 81 without leaving a remainder.
The factors of 81 are:
- 1 (81 ÷ 1 = 81)
- 3 (81 ÷ 3 = 27)
- 9 (81 ÷ 9 = 9)
- 27 (81 ÷ 27 = 3)
- 81 (81 ÷ 81 = 1)
Thus, the complete list of factors of 81 is {1, 3, 9, 27, 81}.
Looking at your options: a) {1, 3, 9, 27, 81} - This is correct. b) {1, 3, 4, 9, 27, 81} - This is incorrect (4 is not a factor). c) {1, 9, 81} - This is incorrect (missing factors 3 and 27). d) {1, 81} - This is incorrect (missing factors 3, 9, and 27).
Therefore, the correct choice is a) {1, 3, 9, 27, 81}.