L1 · The missing part: a + • = c and • + b = c

Learning goal

“I can find the missing part in an addition sentence.”

Part — one piece of a whole number. In 5 + 4 = 9, the parts are 5 and 4.

Whole — the number the parts make together. In 5 + 4 = 9, the whole is 9.

Missing part (•) — the dot stands for a part we do not know yet.

Worked example

Find • in 5 + • = 9. Think of the mat: the whole is 9. One part is 5. Find the other part. Count on from 5: 6, 7, 8, 9. That is 4 counts. So 5 + 4 = 9. The missing part is 4. Check: 5 + 4 = 9 - the parts make the whole.

Check yourself — explain it

Why do we count on from 5?

Paired problem — example still visible

Find • in 4 + • = 7 -> 3 (count on from 4: 5, 6, 7 - 3 counts; check: 4 + 3 = 7)

Faded completion — last step is yours

"6 + • = 10. Count on from 6: 7, 8, 9, 10. That is 4 counts, so the missing part is ___" -> 4

Ready to practise?

8 scored questions with a 3-rung hint ladder. Mastery needs 7/8 plus both gate questions.

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