Grades: 4‒5

Students decompose the factors of two-digit multiplication problems into the sum of their tens and ones by manipulating a dynamic array of base-ten blocks. For example, students might decompose 27 × 39 into the equivalent problem (20 + 7) × (30 + 9). Students compute the partial products in their array and then add them together to find the product of the original problem.

OBJECTIVES

- Students will find products of two-digit numbers by decomposing each number into tens and ones.
- Students will use a rectangular array model composed of base-ten blocks to explore two-digit multiplication problems.
- Students will understand the relationship between a multiplication problem represented in numerical form and the same problem represented with an array.

COMMON CORE CONNECTIONS

Mathematical Practices

(1) Make sense of problems and persevere in solving them; (2) Reason abstractly and quantitatively; (3) Construct viable arguments and critique the reasoning of others; (5) Use appropriate tools strategically; (7) Look for and make use of structure.

Content Standards

4.NBT5