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.
b)
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.