Square Root Progression
The methods outlined below are intended as aids to mental arithmetic in multiplication.
The simple rule for progressing from one square root to another is as follows:-
- Double the Starting Square Root. [Result 1].
- Add the difference between the Starting and Ending Square roots to Result 1 [Result 2].
- Multiply Result 2 by the difference. [Result 3]
- Add Result 3 to the original square to get the final square root.
Example:-
To move from the square root of 9 to the square root of 15.
- Difference between 15 and 9 = 6.
- Double starting square: 9+9 and add difference (6) giving us 24.
- Multiply 24 by difference 6 = 144.
- The square of 9 = 81 + 144 = 225 (square root of 15).
Knowledge of square root progression could be important in determining the factors of some numbers.
For instance, say you had a number like 391. On the face of it, it isn't obvious that 391 has prime factors. But we know that if you add 9 (a perfect square) to 391 we get 400 (a perfect square).
Those facts tell us 391 must have prime factors. See Prime Factors Of A Number. Given 20 is the square root of 400 and 3 is the square root of 9, the answer lies 20 ± 3 which gives 17 and 23 - the factors of 391.
Input the appropriate figures below to explore other numbers.
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TITLE : Square Root Progression
URL : http://www.datedial.com/datSquare_Root_Progression.asp
DESCRIPTION : How we progress from one square root to another.
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