Primary Standard(s)
MAFS.5.NBT.2.5 – Fluently multiply multi-digit whole numbers using the standard algorithm.
Connecting Standard(s)
MAFS.5.NBT.1.2 – Explain patterns in the number of zeros of the product when multiplying a number by powers of 10, and explain patterns in the placement of the decimal point when a decimal is multiplied or divided by a power of 10. Use whole-number exponents to denote powers of 10.
Content Knowledge:
In this Unit, students will focus on developing a standard algorithm for multi-digit multiplication by connecting to prior understanding of place value, multiplication concepts, and partial products. Along with demonstrating understanding of the algorithm, and using place value concepts to justify it, students will also focus on building fluency with it.
In 4th grade, students explored a variety of strategies for multiplying a 1-digit factor by whole numbers up to four digits, and 2-digit factors by 2-digit numbers. The emphasis was on understanding the concept of multiplying multi-digits numbers, as well as using models to visualize the process of multiplication. Students also used their understanding of place value as they decomposed the numbers to create partial products based on the expanded form of factors. In 5th grade, as students work with numbers involving more digits, they may find that area models and partial products become cumbersome. In these situations, a standard algorithm can be a useful tool. For some students, the standard algorithm can become just a series of memorized steps. When that happens, errors occur because students are no longer thinking about the value of the numbers. For this case, it is important students connect to previous methods, use estimation to determine reasonability of products, and verbalize the steps in the algorithm, explaining why they might place a zero or record a regrouping.
GCG 1 – Learning Goal: As a Mathematician, I will be able to Use models to multiply single-digit and multi-digit factors MAFS.5.NBT.2.5
- Step 1: Use estimation to justify reasonableness of products
- Step 2: Use place value models to multiply multi-digit numbers
GCG 2 – Learning Goal: As a Mathematician, I will be able to Find products of multi-digit factors by single and 2-digit factors MAFS.5.NBT.2.5
- Step 1: Use the standard algorithm to multiply multi-digit numbers by a 1-digit multiplier
- Step 2: Use the standard algorithm to multiply multi-digit numbers by a 2-digit factor
- Step 3: Use place value to explain how zeros in factors affect use of the standard algorithm
- Step 4: Problem Solving with multi-digit whole numbers by 2-digit factors
