This skill involves interpreting a two-digit number as tens and ones and combining it with a one-digit addend, including cases in which the ones require composing a new ten (for example, 47 + 6 = 53). Reasoning may be represented with place-value drawings, equations, or an open number line, emphasizing that the added one-digit quantity changes ones and, when necessary, the tens; it does not include adding two multi-digit numbers or extending to more general algorithms.
To add a 2-digit number and a 1-digit number, start with the ones. If the ones make 10 or more, regroup 10 ones as 1 new ten.
Example: Find .
That is ten and ones.
Combine the tens:
The original tens plus the new ten makes tens.
Put the tens and ones together:
So,
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