Squaring numbers in the 100's
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- Choose a number over 100 (keep it low for practice,
then go higher when expert).
- The last two places will be the square of
the last two digits (keep any carry) _ _ _ X X.
- The first three places will be the number plus
the last two digits plus any carry: X X X _ _.
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Example:
- If the number to be squared is 106:
- Square the last two digits (no carry): 6 × 6 = 36: _ _ _ 3 6
- Add the last two digits (06) to the number: 106 + 6 = 112: 1 1 2 _ _
- So 106 × 106 = 11236.
See the pattern?
- If the number to be squared is 112:
- Square the last two digits (keep carry 1): 12 × 12 = 144: _ _ _ 4 4
- Add the last two digits (12) plus the carry (1) to the number:
112 + 12 + 1 = 125: 1 2 5 _ _
- So 112 × 112 = 12544.
With a little practice your only limit will be your ability to square the last
two digits!
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