M2.8.4 For the adult
Missing numbers
What is the missing number in 36 + ? = 50?
What this chapter teaches
To find a missing number, use the opposite operation, then put the answer back in the sum to check. The opposite of + is −, and the opposite of × is ÷.
Three questions to ask
There is no one right wording. Listen for the idea.
- How do you find the missing number in 36 + ? = 50?
- Why is it a good idea to put your answer back in the sum?
- Can you make up a missing number puzzle that uses ×?
After the chapter, the learner can
- Find the missing number in 36 + ? = 50
- Find the missing number in ? × 6 = 42
- Use the opposite operation to check a missing number
What they copy into their notebook
To find a missing number, use the opposite operation. For 36 + ? = 50, do 50 − 36 = 14. For ? × 6 = 42, do 42 ÷ 6 = 7. Then check.