Sometimes a number in a sum is hidden, like 6 + ☐ = 11. The box stands for the missing number. Ask: what do I add to 6 to get 11?
Count up from 6 to 11, or use a fact you know. 6 + 5 = 11, so the missing number is 5. The equals sign means both sides are the same amount.
Worked example
☐ − 4 = 9
- Something take away 4 leaves 9.
- Put the 4 back: 9 + 4 = 13.
Answer:13
Key words
- missing number
- the hidden number in a sum
- equals (=)
- both sides are worth the same
- check
- test your answer in the sum
Practise this
New questions every time.
Common Core-referenced: 1.OA.D.8