Grade 5 · Math · Lesson 6

Long Multiplication (2-digit by 2-digit)

Long multiplication breaks a 2-digit by 2-digit problem into two smaller multiplications, called partial products. You multiply by the ones digit, then by the tens digit, and add the results. The area model shows the same idea as a rectangle split into four boxes.

What this lesson teaches

1Multiply a 2-digit number by a 2-digit number using the standard long-multiplication algorithm
2Write and add the partial products in the correct place-value columns
3Use the area model (box method) to decompose factors and find the same product
4Estimate products by rounding each factor to the nearest ten to check reasonableness

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