Paul uses 1 can of frosting to frost a layer cake. He uses a half can of frosting for a single cake, or a single pan of brownies, or a dozen cupcakes. For Saturday, he needs to have 3 layer cakes, 6 dozen cupcakes, 12 single cakes and 18 pans of brownies ready and frosted for customer pick up. How many cans of frosting will he need? Think carefully first, then make a decision:
He needs 1 can of frosting per layer cake and he needs to make 3 layer cakes so that's 1 * 3 = 3 cans of frosting. There are 6 dozen cupcakes,12 single cakes and 18 pans of brownies for a total of 6 + 12 + 18 = 36 orders. Each of the 36 orders needs 1 / 2 can of frosting so they need 36 * .5 = 18 cans of frosting. He needs 3 cans of frosting for the layer cakes and 18 cans for the remaining items for a total of 3 + 18 = 21 cans of frosting. So, the answer is 21.