Shortcuts On Squaring Two-Digit Numbers Part One
SHORTCUTS ON SQUARING TWO-DIGIT NUMBERS Part One
A. Squaring 2-digit number ending in one
Example One : Square 51
Step One : Take a two-digit number ending in 1, then subtract 1 from it.
51 – 1 = 50
Step Two : Square the difference
50 * 50 = 2500
Step Three : Double the difference in step one 1 and add it to the square in step two
2500 + 100 = 2600
Step Four : Add 1 to the sum in step three
2600 + 1 = 2601
Therefore 51 * 51 = 2601
Example two : Square the number 71
Step one : 71 – 1 = 70
Step two : 70 * 70 = 4900
Step three : 4900 + 140 = 5040
Step four : 5040 + 1 = 5041
Therefore 71 * 71 = 5041
B. Squaring a 2-digit number ending in 2
Example One : Square 62
Step One : Take a two-digit number ending in 2. If the number is 62, the last digit in the square
is 4 . _ _ _ 4
Step two : Multiply the first digit by 4 =è 6 * 4 = 24
The second digit in the produc t will be the next to the last digit in the square. Keep any carry.
_ _ 4 4
Step three: Square the first digit and add the number carried from the previous step.
6 * 6 = 36
36 + 2 = 38
Threfore the square of 62 is 3844
Example two : Square 72
First step : 2 * 2 = 4
Second step : 7 * 4 = 28 =è _ _ 84
Third step : 7 * 7 = 49 ==è 49 + 2 = 51
Therefore 72 * 72 = 5184
C. Squaring a 2-digit number ending in 3.
Example one : Square 53
Step one : Take a two-digit number ending in 3. The last digit of the square will be 9.
Step two : Multiply the first digit by 6. The second digit in the product will be the next number to
The last digit in the square . Keep any carry.
5 * 6 = 30
_ _ 0 9
Step three : Square the first digit and add the number carried from the previous step .
5 * 5 = 25
25 + 3 = 28
Therefore 53 * 53 = 2809
Example two : Square 83
Step one : 3 * 3 = 9
Step two : 8 * 6 = 48
_ _ 8 9
Step three : 8 * 8 = 64
64 + 4 = 68
Therefore 83 * 83 = 6889
SOURCE : MATH POWER by Divina Gracia T. Bandong.