Grade 2 Unit 9
Lesson 2: Fluency Flip
CC BY 2021 Illustrative Mathematics®
Grade 2 Unit 9
Lesson 2: Fluency Flip
CC BY 2021 Illustrative Mathematics®
Directions:
• Partner A holds a card on their forehead without looking.
• Partner B names the number that you can add to the number on the card to get 20.
• Partner A says the number on their card.
Explain how you can use facts you know to find the value of sums and differences you don’t know right away.
Decide if each statement is true or false. Be prepared to explain your reasoning.
8 + 5 = 8 + 2 + 5
8 + 5 = 8 + 2 + 3
Record an equation to represent how you found the unknown addend.
8 + 5 = 10 + 3