Skill: how to practice mental math

Mr. Steve Williams has a sheet that goes beyond 12 x 12
How about 20 x 50?
That's right, you can figure out what
13 x 13
14 x 14

15 x 15
16 x 16 
17 x 17
18 x 18

19 x 19
20 x 20
Wow!  These numbers appear on major tests....  
You can also do mental math with Math Workout on your mobile phone.
How about on a computer?   
GO HERE
http://www.math-play.com/


Math Work out as a phone app