Easily multiply any two digit number by 11.
Example
{% scaleimage l2_example.png float_right %}
Step 1
Add together the digits of the number being multiplied by 11.
3+9=12
Step 2
Place a zero between the two digits of the number being multiplied by 11.
{% scaleimage l2_step1.png %}
Step 3
Add the result from step 1 to the zero in the number from step 2. Don't forget to carry the 1 if there is one.
{% scaleimage l2_step3.png %}