Mental Math Fans? Arthur Benjamin?

Here's a short clip of professor Benjamin  finishing up one of his mental calculation shows. He performs a 5 digit square mentally in about a minute, while simultaneously entertaining his audience. If you like what you see, just type his name in the youtube search, and many of his performances will pop up (TED talks etc.).

Art's 5 digit square

Here's a trick to multiply any two distinct 2 digit numbers. For example, take 78 x 95.  Step 1: 8 x 5= 40 and it ends in 0.  0 will be the last digit of the answer, so it need not be remembered. Take the 4 and add it to the next step 7x5+9x8=111.  Remember the 1 and add 11 to 9x7=74. We can now say our answer is 7,410. Try this with any two digit numbers you like.  IMO, it is ideal to multiply the two numbers with one written directly on top of the other.  All that is required is knowlege of a 10 x 10 multiplication table and practice.