Grade 2 · Computational Fluency
Addition and Subtraction: Facts to 20 and Strategies to 100
Grade 2 computational fluency has two layers: automatic recall of facts to 20 (built on Grade 1 strategies) and flexible multi-digit strategies to 100. The key insight connecting them is place value: 48 + 37 can be solved by adding the tens (40 + 30 = 70), adding the ones (8 + 7 = 15), and combining (70 + 15 = 85). This decompose-and-recompose strategy works because tens and ones operate independently. Students who understand this can compute any two-digit sum mentally.
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
✓Demonstrate fluency with addition and subtraction facts to 20 using strategies: making 10, doubles, bridging
✓Apply mental math strategies for adding and subtracting to 100: friendly numbers, decomposing into tens and ones, compensating
✓Estimate sums and differences to 100 using benchmarks
✓Add up to find the difference: use addition to solve subtraction problems
✓Represent and solve addition and subtraction problems using open number lines, hundred charts, and ten-frames
✓Solve real-life and problem-based addition and subtraction situations