Grade 3 · Computational Fluency
Addition and Subtraction to 1000
Adding three-digit numbers is place value applied to computation. 342 + 256 can be solved as (300+200) + (40+50) + (2+6) = 500+90+8 = 598. The decompose-by-place-value strategy makes the algorithm transparent: it shows WHY the standard algorithm works, not just that it does. Students who understand this connection can compute any multi-digit sum mentally and check answers by estimation.
LESSON VIDEO
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Lesson video
A short walkthrough to play in class or assign for flipped/at-home viewing.
WHAT STUDENTS WILL LEARN
✓Apply flexible strategies for adding and subtracting three-digit numbers: decomposing, friendly numbers, compensating, regrouping
✓Estimate sums and differences to 1000 using rounding and benchmarks
✓Solve multi-step addition and subtraction problems in real-life contexts
✓Use number talks to explore and compare strategies for three-digit computation
✓Check reasonableness of answers using estimation and inverse operations