In this page, we are going to discuss some tricks to multiply a double digit number by 9. We divide this into a few cases:

- The number is a multiple of 11.
- The tens digit is less than the ones digit by one.
- The tens digit is less than the ones digit.
- The tens digit is greater than the ones digit.

In this page, we are going to discuss about case one, where the number is a multiple of 11.

### Condition:

- The multiplicand is a double digit number and also a multiple of 11.
- The multiplier is 9.

__Example 1__
44 x 9 = ?

- Let's say the answer is x. x must be a 3 digits number. The digit in the middle must be 9.

- Multiply the first digit of the multiplicand by 9. In this case, 4 x 9 = 36. The product will be the first and third digit of x (see image below.)

**Example 2**

22 x 9 = ?

- 22 x 9 = __ 9 __
- 9 x 2 = 18

Therefore, 22 x 9 = 198

__Example 3__
88 x 9 = ?

- 88 x 9 = __ 9 __
- 9 x 8 = 72

Therefore, 88 x 9 = 792

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