Question 411947
There are 10 digits (0 -9)
This password is a 4 digit number. You are told the first digit is 5 and that repeats area allowed.

So the format of the password is
5XYZ  where X, Y and Z are any one of 10 digits 0-9.

So you have
{{{OneChoiceTheNumber5 + 10choicesforX * 10choicesForY * 10ChoicesForZ}}}
{{{1 + 10*10*10}}}  
{{{1001}}}