I can't get the answers here
(a) Find the number of ways that Magnus can give out 20 identical stickers to 5 of his friends. (Not everyone has to get a sticker.)
(b) Find the number of ways that Magnus can give out 20 identical stickers to 5 of his friends, if every friend gets at least one sticker.
give them one each to start with then there are 15 stickets left
lie up the stickers divide them into 5 bundles (some bundeles can be empty) the order of the bundles count becasue they are to be given to the five friends who are standing in a row.
You need 4 dividers to do this
so you have 15+4 items = 19
19C4 = 3876 ways.
Use the same logic to get a)
This technique is called stars and bars method if you want to look that up.