The Calendar Problem

Topics: Multiplication, addition, Materials: Calendar, Hundreds chart, pencil and paper, calculator (optional) Common Core: 4.OA.1, 4.OA.3, 4.OA.5, 4.NBT.5, MP1, MP2, MP3, MP6, MP7, MP8 How can you add up these numbers so quickly? Why we love this lesson Simple to launch, instantly engaging and accessible, this puzzle is a beautiful demonstration of the usefulness of multiplication. Not only that, figuring …