SQUARES OF NUMBERS FROM 51 THROUGH 99.
If A is between 50 and 100, then A = 50 + x. Compute a = 50
- x. Then A² = a² + 200x. For example,
63² = 37² + 200×13 = 1369 + 2600 = 3969.
Any Square.
Assume you want to find 87². Find a simple number nearby - a number whose square could be found relatively easy. In the case of 87 we take 90. To obtain 90, we need to add 3 to 87; so now let's subtract 3 from 87. We are getting 84. Finally,
Assume you want to find 87². Find a simple number nearby - a number whose square could be found relatively easy. In the case of 87 we take 90. To obtain 90, we need to add 3 to 87; so now let's subtract 3 from 87. We are getting 84. Finally,
87² = 90×84 + 3² = 7200 + 360 + 9 = 7569.
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