Question

Question 1: To enter their home, the Cepeda family types in a 4 digit

Answer 1

So the first digit could be 0-9.

second is the same 0-9

And the 3rd 0-9 and lastly the 4th 0-9

There is a $\frac{1}{10} *\frac{1}{10} *\frac{1}{10}* \frac{1}{10}$ chance that they will get it right by guessing.

So that means a $\frac{1}{10000}$ chance that they will get it right.

So their are 10000 possible codes.