The purpose of this Number Talk is for students to mentally calculate a product, with which students will work in context in this lesson. The first two products students may know from memory but if not, the idea of doubling 8×4 to find 8×8 can be helpful both for finding the value of 8×8 and for starting a pattern that continues with the next product, 8×8×2, which is double 8×8. The factors 8, 8, and 20 turn out to be the side lengths, in feet, of a standard container used on cargo ships. Students will examine these containers and the ships that carry them throughout the lesson.
Find the value of each expression mentally.