This activity is about multiplying by 11.
Multiplying by 11 is easy for most facts.
Let's look at the eleven times table below:
1 × 11 = 11
2 × 11 = 22
3 × 11 = 33
4 × 11 = 44
5 × 11 = 55
6 × 11 = 66
7 × 11 = 77
8 × 11 = 88
9 × 11 = 99
10 × 11 = 110
11 × 11 = 121
12 × 11 = 132
For all the facts up to 9 × 9, we simply double the digit of the number we are multiplying by 11.
For 10 × 11, we can use place value to multiply by 10 moving each digit one place to the right.
For 11 × 11 and 12 × 11, you need to memorise the facts!
Let's try an example question together!
Example
A cookie has 11 chocolate chips.
How many chocolate chips do 9 cookies have?
What is 9 times 11?
Answer
Using our pattern, we know that nine lots of eleven is ninety-nine.
9 × 11 = 99
What is 11 times 9?
11 × 9 = 99
9 × 11 = 99
That's it!
So long as we know our eleven times table, this activity will be easy!
How do you feel about your elevens?