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3-N-2-8

Page history last edited by Tashe Harris 6 years, 2 months ago

3.N.2.8 Use strategies and algorithms based on knowledge of place value, equality and properties of addition and multiplication to multiply a two-digit number by a one-digit number.

In a Nutshell

Students come to third grade having an understanding of place value and equality. In third grade, their knowledge of those concepts is continued. This objective will take that knowledge and show how it can be used to solve multi-step problems.

Student Actions	Teacher Actions
Make conjectures when solving complex problems based on their prior knowledge of multiplication and regrouping. Demonstrate procedural fluency by accurately identifying properties of addition and multiplication when solving. Develop a flexible understanding by applying what they know about place value to solve two-digit numbers by one-digit one-digit numbers. For example, 23 x 4, is multiplying 2 tens by 4 and 3 ones by 4. Communicate mathematically to the teacher and other students.	Pose purposeful questions to spark discussion and thinking. Questions may include: What other mathematical strategies can we use to solve our problem? Are there other ways we can solve? How can we prove our answer? Facilitate mathematical discourse to help students develop their ideas and make connections when problem-solving. Support productive struggle as students challenge themselves to make connections to other mathematical concepts, such as basic multiplication, addition with regrouping, and decomposing numbers based on place value.
Key Understandings	Misconceptions
Their understanding of place value and basic multiplication facts will help them solve two-digit by one-digit multiplication. Multiplication and addition are alike in that their answers are the same no matter the order of the addends (in addition) or factors (in multiplication).	They do not need to regroup. For example: Students may think 27 x 3 = 621 rather than 81. They multiply the number that is regrouped versus adding it. For example: If they have the problem: 27x3. They will multiply 7x3 and get 21. They then drop the one and carry the 2. Next, they multiply 3x2=6, but then multiply that by 2 (instead of add 2). They then get the answer 121 versus the correct answer, 81.