Multiplication Tables 11 and 12
The 11 and 12 tables look scary but are easy. 11 × anything 1-9: write the digit twice. 11 × 3 = 33. 11 × 7 = 77. 11 × 9 = 99. Only 11 × 10 and up break the pattern. The 12 table uses 10× + 2×. 12 × 4 = 40 + 8 = 48. 12 × 7 = 70 + 14 = 84.
The Core Idea
11x (single digit): repeat the digit. 11×2=22, 11×3=33, ..., 11×9=99. 11×10=110. 11x (double digit): add the two digits and stick between. 11×23 = 2(2+3)3 = 253. The 12x table: break into 10x + 2x. 12 × 8 = 80 + 16 = 96.
12 Table
12x1=12, 12x2=24, 12x3=36, 12x4=48, 12x5=60, 12x6=72, 12x7=84, 12x8=96, 12x9=108, 12x10=120, 12x11=132, 12x12=144. The 12 table comes up a lot because of 12-inch feet, 12-hour clocks, dozens.
What is 11 × 6?
Going Deeper
Why does 11x single-digit repeat? Because 11 = 10 + 1. So 11 × 6 = 10×6 + 1×6 = 60 + 6 = 66. The digit just lines up. Understanding WHY the shortcut works is more powerful than just memorizing it.
11 Shortcut
12 Breakdown
12 × 9?
12 × 12?
The 11 × Two-Digit Trick
Here is a magic trick for multiplying 11 by a two-digit number 10-99. For 11 × 23: separate the digits of 23 (2 and 3), ADD them (2+3=5), then put the sum BETWEEN the digits: 2__5__3 → 253. Check: 23 × 11 = 23 × 10 + 23 = 230 + 23 = 253 ✓. Try 11 × 45: digits 4 and 5, sum 9, result 495. Try 11 × 62: digits 6 and 2, sum 8, result 682. EXCEPTION: when the digit sum is 10 or more, carry the 1 to the left digit. 11 × 78: 7 and 8, sum 15 — write the 5, carry 1 into the 7 → 858. Use this trick in your head to astonish people.
11 Magic Trick
Have someone pick any two-digit number. In your head, use the 11× trick to multiply it by 11. Announce the answer. Have them check with a calculator. Do this 5 times — you will look like a math wizard.
Without a calculator, what is 11 × 52?
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