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Squares & Roots

STRATEGY

Start from a square you already know and adjust up or down.

  1. 1Going up (e.g. 21²): start from 20² (400), then add both bases (20 + 21)
  2. 2Going down (e.g. 19²): start from 20² (400), then subtract both bases (20 + 19)
EXAMPLE
21²
→ 20² = 400 → 400 + 20 + 21 = 441