2.2 Combinations

Ex 1 (a) A bag has 13 marbles in it, how many ways can you remove 3 marbles from the bag, one at a time?

(b) How many ways can you reach in and grab 3 marbles at once?

(c) There are 6 red, 4 blue, and 3 green marbles in the bag, how many ways can you grab one of each at the same time?

(d) How many ways can you grab 3 non-blue marbles at the same time?

(e) How many ways can you grab 3 marbles at the same time and have at least one be green?

A combination is the number of ways you can create a group from a larger group. A combination is a permutation where you don’t care about the order.

‘n choose r’

Ex 2 (a) A gardener bought 5 geraniums, 3 rose bushes, and 4 evergreens from a nursery that had 14 geraniums, 12 rose bushes, and 5 evergreens. How many choices did the gardener have?

(b) What if the gardener wanted 5 geraniums and 3 roses or 4 evergreens?

p.279#2-9, 11-18