Here's a simple trick to square any
number that ends in 1.
- Subtract 1 from the number.
- Square the difference. (Squaring of such number is easy as it ends in ‘0’)
- Add the difference twice to its square.
- Add 1.
Example: If
the number to be squared is 61
1. Subtract
1=> 61 - 1 = 60.
2. Square
the difference => 60 × 60 = 3600.
3. Add
the difference twice to its square => 3600 + 60 + 60 = 3720.
4. Add
1 => 3720 + 1 = 3721.
812 =?
1) 81
- 1 = 80 (Subtract 1).
2) 802
= 6400 (square the difference).
3) 6400
+ 80 + 80 = 6560 (add the difference twice to its square).
4) 6560
+ 1 = 6561 (add 1)
So, 812
= 6561
If the number to be squared is a
3-digit number, let’s say 121
1) 121
- 1 = 120 (Subtract 1).
2) 1202
= 14400 (square the difference).
3) 14400
+ 120 + 120 = 14640 (add the difference twice to its square).
4) 14640
+ 1 = 14641 (add 1)
So, 1212
= 14641
2512 =?
1) 251
- 1 = 250
2) 2502
= 62500
3) 62500
+ 250 + 250 = 63000
4) 63000
+ 1 = 63001
So, 2512
= 63001
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