If Zack fills two bird feeders, and each holds 2 1/2 cups of seed, that means that combined they will hold 5 cups of bird seed. I cup can be divided into fourths (or 1/4), this means that for every cup of bird seed Zack will need four scoops.
Here is an equation to show the answer:
5 cups × 4 (the number of scoops in a cup) = 20 scoops needed to fill both both bird feeders.
