Here is the complete multiplication table of 28 from 1 to 20, with a quick memory tip.
28 is a perfect number — a rare number that equals the sum of its proper divisors: 1+2+4+7+14 = 28. Only 4 perfect numbers exist below 10,000: 6, 28, 496, 8128.
28 × 1 = 28 28 × 2 = 56 28 × 3 = 84 28 × 4 = 112 28 × 5 = 140 28 × 6 = 168 28 × 7 = 196 28 × 8 = 224 28 × 9 = 252 28 × 10 = 280
28 × 11 = 308 28 × 12 = 336 28 × 13 = 364 28 × 14 = 392 28 × 15 = 420 28 × 16 = 448 28 × 17 = 476 28 × 18 = 504 28 × 19 = 532 28 × 20 = 560
28 = 30 − 2, so: 28 × n = (30 × n) − (2 × n)
Example: 28 × 7 = (30×7) − (2×7) = 210 − 14 = 196 ✓
28 × 8 = (30×8) − (2×8) = 240 − 16 = 224 ✓
This shortcut works for any multiple of 28!
28 × 15 = (30×15) − (2×15) = 450 − 30 = **420**
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