Shortcut to Multiplying By 12

So how does the 12's shortcut work?                                       

Let's take a look.
12 X 7

The first thing is to always multiply the 1 of the twelve by the
number we are multiplying by, in this case 7. So 1 X 7 = 7.

Multiply this 7 by 10 giving 70.


Now multiply the 7 by the 2 of twelve giving 14. Add this to 70 giving 84.

Therefore 7 X 12 = 84

Let's try another:
 17 X 12

Remember, multiply the 17 by the 1 in 12 and multiply by 10

(Just add a zero to the end)
1 X 17 = 17, multiplied by 10 giving 170.

Multiply 17 by 2 giving 34.
Add 34 to 170 giving 204.
So 17 X 12 = 204

lets go one more
24 X 12


Multiply 24 X 1 = 24. Multiply by 10 giving 240.

Multiply 24 by 2 = 48. Add to 240 giving us 288
24 X 12 = 288