MAFS.1.OA.4.8 Determine the unknown whole number in an addition or subtraction equation relating to three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = [] – 3, 6 + 6 = [].
Cognitive Complexity Level: 1-Recall
[divider] [/divider] Students are able to…
- Solve problems with manipulatives and write equations to represent their work
- Solve for the unknown in various positions
- Explain their thinking
[divider] [/divider] Students are able to…because teachers:
- Model writing equations to represent student work
- Provide opportunities for students to write equations that represent their strategy
- Provide equations to solve where the unknown is in different positions
[divider] [/divider] Questions to ask students:
- Ask: Write an equation to match this problem: I have 9 toy cars on the table. Some of the cars rolled onto the floor. Now I have 4 toy cars on the table. How many toy cars rolled onto the floor? Explain your thinking.
- Sample answer that indicates understanding:9 – __ = 4 ; This equation matches because I started with 9. I did not know how many cars rolled off the table so I drew a blank. I have 4 left on the table so I placed a 4 on the other side of the equal sign.
[divider] [/divider] Additional Resources:
Additional in depth content knowledge
Video: Khan Academy – Find Missing Number Practice
[divider] [/divider] Sample Formative Assessment Tasks:
[divider] [/divider] Resources/Tasks to Support Your Child at Home:
- Khan Academy Video – Relating Addition and Subtraction
- Task: Use playing cards (Ace – 9) and +, -, and = cards created from paper. Player one creates a true equation using the cards and symbols. Player two reorganizes cards to find the remaining 3 related facts.
- Task: Pose various addition problems with unknown addends and encourage your child to use the inverse operation of subtraction to solve for the missing amount.