Maria ate 20% of a box of cereal that weighed 300 grams. How many grams of cereal did she eat? A tape diagram. Maria ate 20 percent out of 100 percent of a box of cereal. She ate question mark out of 300 percent of a box of cereal. The percent in the problem written as a ratio: part =____ whole = _____ 100 multiplied by _____ is equal to 300. 20 muliplied by ______ is equal to .