From EngageNY.org of the New York State Education Department. Grade 3 Mathematics Module 3, Topic F, Lesson 21. Internet. Available from https://www.engageny.org/resource/grade-3-mathemat...; accessed 21/Oct/2015.
Frederick buys a can of 3 tennis balls. The empty can weighs 20 grams, and each
tennis ball weighs 60 grams. What is the total weight of the can with 3 tennis
balls?