Big Ideas: Compose and decompose base-10 units. Use place value understanding and properties of operations to perform multi-digit arithmetic visual representations. Students use rectangular arrays to multiply 2-digit by 1-digit and 2-digit by 2-digit whole numbers. Students develop, discuss, and use efficient, accurate, and generalization methods to compute products of multi-digit whole numbers. They apply their understanding of models for multiplication (equal-sized groups, arrays), place value, properties of operations, and the distributive property. Vocabulary: factor pairs, multiples, equation, rectangular array Special Materials: graph paper, optional base-10 blocks, optional