lane mcbride
06-13-2005, 04:55 AM
Some of you may be familiar with this already, but if not here goes. It's a little math trick you can do to impress your friends or make mental math a little easier.
the first one involves squaring numbers (forgive me if this is difficult to understand... it's not too easy to explain without a pencil and paper)... there is another one that works for multiplication not involving squares, if anybody is interested, I would be happy to explain that too.
for example: if you take 99 and you want to find out what it is squared (99 x 99) you take the difference from 100 of the number (which is 1 in this case) you then subtract that from the number so 99-1 = 98... now you square the difference you came up with (again 1) and put it on the end of the 98... so 99 squared is 9801.
another example 97 x 97. the difference from 100 is 3
subtract that from 97--> 97-3 =94
(now square the 3 and put it on the end of the 94)--> so 9409.
for numbers over 100 you add the difference. example:
103
difference from 100 is 3 103 + 3 = 106
now square the 3 and put it on the end 106(09)
so 10609 is 103 squared.
for numbers close to 50 you take the difference from fifty and divide by two before adding the suffix
example 48
difference from 50 is 2 48-2 =46 --> 46/2 = 23
now add the suffix to 23 so 23(04)
48 squared is 2304
53 difference from 50 is 3 53 + 3 = 56--> 56/2 = 28
now add the suffix (3 squared) to 28--> 28(09)
53 squared is 2809.
the first one involves squaring numbers (forgive me if this is difficult to understand... it's not too easy to explain without a pencil and paper)... there is another one that works for multiplication not involving squares, if anybody is interested, I would be happy to explain that too.
for example: if you take 99 and you want to find out what it is squared (99 x 99) you take the difference from 100 of the number (which is 1 in this case) you then subtract that from the number so 99-1 = 98... now you square the difference you came up with (again 1) and put it on the end of the 98... so 99 squared is 9801.
another example 97 x 97. the difference from 100 is 3
subtract that from 97--> 97-3 =94
(now square the 3 and put it on the end of the 94)--> so 9409.
for numbers over 100 you add the difference. example:
103
difference from 100 is 3 103 + 3 = 106
now square the 3 and put it on the end 106(09)
so 10609 is 103 squared.
for numbers close to 50 you take the difference from fifty and divide by two before adding the suffix
example 48
difference from 50 is 2 48-2 =46 --> 46/2 = 23
now add the suffix to 23 so 23(04)
48 squared is 2304
53 difference from 50 is 3 53 + 3 = 56--> 56/2 = 28
now add the suffix (3 squared) to 28--> 28(09)
53 squared is 2809.