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# CCSS.Math.Content.2.NBT.B.9 - Explain why addition and subtraction strategies work, using place value and the properties of operations.

Authors: National Governors Association Center for Best Practices, Council of Chief State School Officers

Title: CCSS.Math.Content.2.NBT.B.9 Explain Why Addition And Subtraction Strategies Work,... Number and Operations in Base Ten - 2nd Grade Mathematics Common Core State Standards

Publisher: National Governors Association Center for Best Practices, Council of Chief State School Officers, Washington D.C.

(Page last edited 10/08/2017)

1. Adding to Subtract; worksheet - Good whole class activity; discuss the various strategies children used to solve the problems.
2. Addition to 50 - Worksheet or whole class IWB activity; use various strategies to find the missing number.
3. Draggable Math - Good activity for IWB or whole class; choose level of question, then answer it.
4. Mathsheet Generator - Use this generator to create your own worksheet; set the parameters yourself. Ask students to share their strategies for answering the problems.
5. Missing Numbers - Activity for IWB or whole class. Input your own parameters.
6. Related Addition Facts - Online quiz; write the related addition fact.
7. Related Subtration Facts - Online quiz; write the related asubtraction fact.
8. Subtraction Strategies - Article with explanations of various strategies; good for whole class or IWB. Click on the link at the bottom for practice exercises.
9. What two numbers add up to 50? - Online interactive quiz/game format. Good for whole class activity. Ask students to explain their strategies in this game of cards.

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