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Interpret addition as joining

Addition represents joining two quantities to find their combined amount, with the quantities as addends and the result as the sum. For whole-number situations within 20, this understanding connects joining contexts, part–part–whole diagrams, drawings, number lines, and equations such as 7+5=127+5=12, while distinguishing each part from the total and interpreting the equal sign as “has the same value as.” Larger-number generalizations, negative numbers, and formal algebraic treatment are not included.

Detailed Explanation: Interpret addition as joining

When you join two groups, you put them together to find how many there are altogether. This is addition.

Example: Mia has 7 crayons. She gets 5 more crayons. How many crayons does she have now?

  1. Find the two parts.

    • First group: 7 crayons
    • Second group: 5 crayons
  2. Join the groups.
    Count all the crayons:

    🖍️🖍️🖍️🖍️🖍️🖍️🖍️ + 🖍️🖍️🖍️🖍️🖍️

  3. Write an addition equation.
    The numbers being joined are called addends:

7+5=127+5=12
  1. Find the sum.
    The answer, 1212, is called the sum. It tells how many crayons there are altogether.

    You can also start at 7 on a number line and count forward 5 steps: 8, 9, 10, 11, 12.

The equal sign means “has the same value as.” So, 7+57+5 has the same value as 1212.

Learn by doing: Interpret addition as joining

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Addition - Whole Number - Within 10


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