எந்த 2-இலக்க எண்ணையும் 11-ஆல் பெருக்கவும்
Multiply Any 2-Digit Number by 11
Write the first digit, add the two digits in the middle, write the last digit. That's it. 11 multiplication becomes instant — and you'll understand exactly why.
Let's Learn
What you will learn today
Multiply any 2-digit number by 11 instantly using the split-and-sum pattern.
What is 11 × 1? × 2? × 3? × 4? × 5?
11, 22, 33, 44, 55. Notice the pattern: each digit repeats. What about 11 × 12? 11 × 23? 11 × 45? These are harder — but there is still a beautiful pattern hiding.
Here is the secret for multiplying any 2-digit number by 11: write the first digit, write the sum of both digits in the middle, write the last digit. Three positions, two additions — done in under 2 seconds.
11-ஆல் பெருக்கல்: முதல் இலக்கம், இரண்டின் கூட்டல், கடைசி இலக்கம்.
📐 Simple case: 24 × 11
Digits of 24: first=2, last=4.
- 1Write the first digit: 2
- 2Middle: sum of digits 2+4 = 6. Write 6.
- 3Write the last digit: 4
- 4Result: 264. And 24 × 11 = 264 ✓
📐 Simple case: 53 × 11
Digits of 53: first=5, last=3.
- 1First: 5
- 2Middle: 5+3 = 8
- 3Last: 3
- 4Result: 583. Check: 53 × 11 = 53 × 10 + 53 = 530+53 = 583 ✓
What if the middle sum is ≥ 10? (Carry case)
When the two digits add to 10 or more, you need to carry. The middle position gets the units digit of the sum, and the carry adds to the first digit.
- 85 × 11: digits 8 and 5. Sum: 8+5=13.
- Middle position gets 3 (units of 13)
- Carry 1 to the first digit: 8+1=9
- Last digit stays: 5
- Result: 935. Check: 85×10+85 = 850+85 = 935 ✓
📐 Carry case: 96 × 11
Digits: 9 and 6. Sum: 9+6=15.
- 1Middle: units of 15 = 5
- 2Carry 1 to first digit: 9+1=10 → the answer has 4 digits!
- 3Result: 1056. Check: 96×11 = 960+96 = 1056 ✓
Why does this work?
11 = 10 + 1. So AB × 11 = AB × 10 + AB × 1 = AB0 + AB. When you add AB0 + AB, the tens digit of AB0 and the units digit of AB overlap — their sum is the middle digit. The carry moves into the hundreds position. This is exactly what the shortcut computes.
Try: 34 × 11
What are the three steps? What is the answer?
Challenge Round
Challenge: 78 × 11
Apply the rule. The middle sum will be ≥ 10 — handle the carry correctly.
×11 rule: first digit | sum of digits (with carry if ≥10) | last digit. When sum ≥ 10, add 1 to the first digit and use the units of the sum as the middle.
↪ Next: Squaring numbers ending in 5 — a two-step rule for instant squares.
Key Points
முக்கிய குறிப்புகள்
- ✓AB × 11 = A | (A+B) | B
- ✓If A+B ≥ 10, carry 1 to A: (A+1) | units(A+B) | B
- ✓Why: 11 = 10+1, so AB×11 = AB×10 + AB = overlap addition
- ✓Works for any 2-digit number
Glossary
சொல் அகராதி
Split method
பிரி முறை
Carry
கடந்து சேர்
Middle digit
நடு இலக்கம்
Sum
கூட்டுத்தொகை
Practice Activities
Quizவினாடி வினா
Answer each question to check your understanding.
What is 63 × 11?
Fill in the Blanksஇடைவெளி நிரப்புக
Type the missing word and press Check or Enter.
Type the missing word and click Check.