1) How many different ID cards are possible if there are six digits (slots) on the card and repetition of numerals is allowed? Therefore, this six digit ID is now allowed: 429468
2) Joe has 12 different books in the box. He is to choose 5 of them and arrange them on the shelf. In how many ways can he do this?
3) The exam has 15 questions. Student is inquired to choose only 10 of them, and reply only those 10 out of 15. In how many ways those ten questions can be selected?