How many pounds of pork roast with 15-percent shrinkage should be purchased to serve 600 portions weighing three ounces each?

Here's how to calculate the amount of pork roast to purchase:

1. Calculate the total weight needed before shrinkage:

* 600 portions * 3 ounces/portion = 1800 ounces

* 1800 ounces / 16 ounces/pound = 112.5 pounds

2. Account for shrinkage:

* 112.5 pounds / (1 - 0.15) = 132.35 pounds

Therefore, you should purchase approximately 132.35 pounds of pork roast to serve 600 portions after accounting for 15% shrinkage.