How Do You Express the Number of Security PINs in Logarithmic Form?

[BlackOut07]

Homework Statement

A security PIN code is four digits long. Each digit could have the value 0 to 9. if an office building needs 10 security PINs, express the number of codes in logarithmic form with base 10

The Attempt at a Solution

y=4log(x-10)

I don't know how to do the question, but my best attempt produced what you see above.

4 represents the # of digits.
x-10 because of the range 0-9.

 

[HallsofIvy]

What was your reasoning behind "x- 10"?

There are $10^1= 10$ one digit numbers, 0 to 9.

There are $10^2= 100$ two digit numbers, 00 to 99.

There are $10^3= 1000$ three digit numbers, 000 to 999.