Question

4. Social Security numbers are in the form ###-##-####, where each symbol represents a number 0 through 9. How many Social Security numbers are possible using this format?

Answer 1

Since we have 10 choices in each symbol of the security number and they caan be repetitions we have a total of:

$\begin{gathered} 10\cdot10\cdot10\cdot10\cdot10\cdot10\cdot10\cdot10\cdot10=10^9 \\ =1000000000 \end{gathered}$

Therefore we have a total of 1,000,000,000 possible social security numbers.