Arrangements with divisibility constraints

Questions asking for arrangements of digits (not letters) from a number with repeated digits, where the resulting number must satisfy a divisibility or parity condition (e.g., even numbers).

1 questions

CAIE S1 2015 June Q7
7
  1. Find how many different numbers can be made by arranging all nine digits of the number 223677888 if
    1. there are no restrictions,
    2. the number made is an even number.
  2. Sandra wishes to buy some applications (apps) for her smartphone but she only has enough money for 5 apps in total. There are 3 train apps, 6 social network apps and 14 games apps available. Sandra wants to have at least 1 of each type of app. Find the number of different possible selections of 5 apps that Sandra can choose.