2.12.a
Explain that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
Khan Academy ResourcesAdd and subtract on the number line word problemsSubtraction word problems within 100Subtract within 1,000 using place value blocksSubtract on a number line2-step subtraction word problems within 100Find the missing number (add and subtract within 100)Estimate to add multi-digit whole numbersAdd on a number line2-step addition word problems within 100Add within 1,000 using place value blocksAdd using groups of 10 and 100Select strategies for adding within 100Break apart 3-digit addition problemsSelect strategies for adding within 1000Addition word problems within 100Breaking apart 3-digit addition problemsAdding and subtracting on number line word problemsSubtracting 3-digit numbers (no regrouping)Adding 10 or 100Adding 1s, 10s, and 100sSubtraction word problem: basketballAdding and subtracting on number lineAddition using groups of 10 and 100Adding two digit numbers on a number lineAddition word problem: horsesSubtracting 1s, 10s, and 100sMulti-step subtraction word problemAdding 3-digit numbers (no regrouping)Subtracting 1, 10, or 100Multi step addition word problemSubtracting with place value blocks (regrouping)Subtraction word problem: crayons

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