Skill: Add within 20

Explanation and Free Practice Resources

Addition within 20 represents joining or increasing whole-number quantities and finding an unknown total or part when the sum is no greater than 20. Quantities can be related through part–part–whole diagrams, ten-frames, number lines, and equations, with reasoning based on counting on, making ten, doubles, and the commutative relationship between addends rather than treating order as significant. This scope does not include multi-digit addition or formal regrouping algorithms; it establishes foundations for place-value-based computation.

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Detailed Explanation: Add within 20

Addition means joining two groups to find how many there are altogether.

Solve $8+5$ :

Start with $8$ .
Make the $8$ into $10$ by taking $2$ from the $5$ .
There are $3$ left from the $5$ , because $5=2+3$ .
Add the parts: $10+3=13$ .

So,

8+5=8+2+3=10+3=13

The total is $\boxed{13}$ .

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Ten Groups - Add, With Carry, Less than 20

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