11s multiplication facts
11s Multiplication Facts in Grade 4 Saxon Math Intermediate 4 gives students a memorable shortcut: when multiplying any single-digit number by 11, simply repeat the digit twice to form the answer. So 11 x 5 = 55, 11 x 9 = 99, and 11 x 3 = 33. The chapter also reinforces multiplying by 10 through place value: multiplying by 10 shifts every digit one position to the left, equivalent to appending a zero. For example, 52 x 10 = 520. Students are cautioned that the repeat-the-digit trick works only for single-digit multipliers — it does not apply to two-digit numbers like 12.
Key Concepts
Property For single digit numbers, the product of the number and 11 is the digit repeated twice.
Example 1. $11 \times 5$: Repeat the digit 5 twice to get 55. So, $11 \times 5 = 55$. 2. $11 \times 9$: Repeat the digit 9 twice to get 99. So, $11 \times 9 = 99$.
Explanation Multiplying by 11 with a single digit is like seeing double! Just take the digit you are multiplying and write it down twice to get your answer. For example, multiplying by 3 gives you 33. This cool pattern makes these facts super easy to remember and solve in a flash. It's a fun party trick!
Common Questions
What is the shortcut for multiplying by 11 with single-digit numbers?
Repeat the single digit twice. For example, 11 x 6 = 66, 11 x 9 = 99, 11 x 4 = 44.
Does the 11s trick work for two-digit numbers?
No. The repeat-the-digit trick only works for single-digit multipliers 1 through 9. For 11 x 12, you need a different strategy.
Why does multiplying by 10 just add a zero?
Multiplying by 10 shifts each digit one place value to the left. The zero fills the now-empty ones place as a placeholder. For example, 23 x 10 = 230.
What is 11 x 7?
Repeat the digit 7 twice: the answer is 77.
How does knowing 11 x 5 = 55 help check a multiplication answer?
If a ticket costs 11 dollars and 5 people attend, the total should be 55 dollars. You can verify quickly by applying the repeat-digit rule.