Missing-part word problems involve determining an unknown quantity in a joining, separating, or part–part–whole situation, with quantities generally within 20. The learner interprets the relationship between the known parts and whole, represents it with a bar model, number line, or equation such as □ + 7 = 12 or 12 − 7 = □, and understands addition and subtraction as related operations rather than choosing an operation from keywords; multi-step problems, larger numbers, and generalized algebraic treatment are not included.
A missing-part problem gives you the whole and one part. You find the part that is missing.
Example:
There are 12 apples. Seven apples are red, and the rest are green. How many apples are green?
You can show the problem with a bar model:
Write an equation:
Think: “What number goes with 7 to make 12?” Count on from 7:
That is 5 numbers, so:
The missing part is 5 green apples.
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