Mental MultiplicationThe methods outlined below are intended as aids to mental arithmetic in multiplication utilizing fundamental knowledge of square root.If you wanted to find the product of two EVEN or two ODD numbers you simply find the square of the mean of the two numbers and subtract the square of half the difference between the two numbers. For instance, to find the product of 17 and 23 we subtract the square of half the difference (3² = 9) from the squared mean (20² = 400). The result is 400  9 = 391. Remember, only EVEN numbers by EVEN numbers and ODD numbers by ODD numbers. Odd Numbers
Even Numbers
An interesting twist is that in special cases we can have an all squares result. For instance :
Input either EVEN or ODD numbers below. As an extension of the application of the above method please see
 
 
