Alright, so we'd use the combinations with repetition formula, so we choose from 4 schools to distribute to and distribute 8 blackboards. It's then
( 8+4-1)!/8!(4-1)!=11!/(3!*8!)=165
For at least one blackboard, we first distribute 1 to each school and then have 4 blackboards left, getting (4+4-1)!/4!(4-1)!=7!/(4!*3!)=35
Celia is making cookies for her neighborhood. She plans to make 9 batches of 13 cookies, but she makes more cookie dough than she planned to and adds 6 cookies to each batch. After they bake, she takes them out of the oven and takes 7 cookies from each tray to keep for herself. How many cookies will be left to distribute among her neighbors?
Hope this helps!
7, 8, 9, 10, or 11 are all natural numbers between 6-12.
