The set of all 3-digit numbers made using only the digits 1 and 2 (each can be used, of course, more than once.)

111, 112, 121, 122, 211, 212, 221, 222

Answer: Total number of 3-digit numbers formed by using 1,2 are 8

Step-by-step explanation:

Consider that there are three blanks and such that each blank has to be filled by either any one of the two numbers i. e., 1,2.

Since each blank can be filled in 2 ways (repetition of digits are allowed),

Total number of 3-digit numbers formed by using 1,2 are

= (2) (2) (2) = 8

Total number of 3-digit numbers formed by using 1,2 are 8