Question

How many numbers not exceeding $1000$ can be made using the digits $1,2,3,4,5,6,7,8,9,$ if repetition is allowed.

Answer 1

$1,2,3,4,5,6,7,8,9$

One digit number can be formed $=9$

Two digit number can be formed $=9$ $\times$ $9=81$

Three digit number can be formed $=9$ $\times$ $9$ $\times$ $9=729$

Total $=9+81+729=819$