Question

10. A social security number contains nine digits, such as 799-23-5675. How many different social security numbers can be formed?

Answer 1

Given:

A social security number contains nine digits.

As there are 10 digits from 0 to 9.

There are 9 positions and every position has 10 possibilities.

If repetition is allowed the number of ways are,

$\begin{gathered} \text{Number of ways=10}\times10\times10\times10\times10\times10\times10\times10\times10 \\ =10^9 \\ =1000000000 \end{gathered}$

Answer: the number of ways are,

$1000000000$