Answer:
If digits can be repeated: 36
If the digit can not be repeated: 30
Step-by-step explanation:
If digits can be repeated:
On the first and second place we have 6 digits to choose from.
Therefore we have 6 · 6 = 36 two-digit numbers.
[tex]\begin{array}{c|c|c|c|c|c|cc}11&41&51&71&81&91&&\to6\\14&44&54&74&84&94&&\to6\\15&45&55&75&85&95&&\to6\end{array}\\\vdots\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad6\\\begin{array}{c|c|c|c|c|c|cc}19&49&59&79&89&99&&\to6\end{array}\\.\\.\qquad\qquad\ \ \ \ 6[/tex]
If the digit can not be repeated:
On the first place we have 6 digits to choose from and on the second place we have 5 digits to choose from.
Therefore we have 6 · 5 = 30 two-digit numbers.
