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Multiply two-digit numbers by two-digit numbers.
Students have seen the area model, the partial products algorithm, and the standard algorithm strategies with two-digit by two-digit multiplication in Grade 4. However, because two-digit by two-digit multiplication is both more complex than all of the cases students saw in Lesson 5 and more closely related to the new cases they’ll see in Grade 5, a whole day has been dedicated to this case to solidify the standard algorithm with this case before moving on to more cognitively complex and new cases in later lessons.
If you need to adapt or shorten this lesson for remote learning, we suggest prioritizing Anchor Task 2 (benefits from worked example) and Anchor Task 3 (can be done independently). Find more guidance on adapting our math curriculum for remote learning here.
1. Here are two ways to find the area of a rectangle that is 23 units by 31 units.
2. You might be familiar with different ways to write multiplication calculations. Here are two ways to calculate 23 x 31.
a. In Calculation A, how are each of the partial products obtained? For instance, where does the 3 come from?
b. In Calculation B, how are the 23 and 690 obtained?
c. Look at the area models in #1. Which area model corresponds to Calculation A? Which one corresponds to Calculation B?
d. How are the partial products in Calculation A and the 23 and 690 in Calculation B related to the numbers in the area models?
1. Label the area model to represent 37 x 49 and to find that product.
2. Here are two ways to calculate 37 x 49. Each number with a box gives the area of one or more regions in the area model.
Estimate the following products. Then solve using the standard algorithm. If you get stuck, use an area model and/or the partial products algorithm to help.
Solve. Show or explain your work.
Grade 5 Mathematics > Module 2 > Topic B > Lesson 5 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..Modified by Fishtank Learning, Inc.
Grade 5 Mathematics > Module 2 > Topic B > Lesson 6 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..Modified by Fishtank Learning, Inc.
Ashley drew an area model to find the value of 85 x 17.
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