To square a number ending in nine; e.g. 29, 59, 129, ..., first square the next number that is ending in zero, and then subtract both the number and the next number from it.
Example 1:
To square 29 (29^2):
29: the number
30: the next number
29^2 = 30^2 - (29 + 30) = 900 - 59 = 841
Example 2:
To square 69 (69^2):
69: the number
70: the next number
69^2 = 70^2 - (69 + 70) = 4900 - 139 = 4761
Example 3:
To square 129 (129^2):
129: the number
130: the next number
129^2 = 130^2 - (129 + 130) = 16900 - 259 = 16641
Example 1:
To square 29 (29^2):
29: the number
30: the next number
29^2 = 30^2 - (29 + 30) = 900 - 59 = 841
Example 2:
To square 69 (69^2):
69: the number
70: the next number
69^2 = 70^2 - (69 + 70) = 4900 - 139 = 4761
Example 3:
To square 129 (129^2):
129: the number
130: the next number
129^2 = 130^2 - (129 + 130) = 16900 - 259 = 16641
No comments:
Post a Comment