# From the digits 1, 2, 3, 4, 5, 7, 9, how many numbers of 3 digits can be formed if repetition is allowed in a number?

${7}^{3} = 343$
The first digit of the 3-digits can take 7 distinct values: 1, 2, 3, 4, 5, 7, 9. As repetition is allowed, the second digit can also take 7 distinct values, and the third can take 7 distinct values aswell, giving a total of $7 \cdot 7 \cdot 7 = 343$ distinct combinations of numbers.