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(*) Squaring A Number In The Range
(40 – 49):
A.
This method comes from algebra:
(50 – a)2 = 100(25 – a) + a2
B. Using numbers instead of
variables we get the following:
1.
Find the difference between the number and 50.
2.
Square the result of step 1 and write it down (make sure it takes up 2
place values).
3.
Subtract the result of step 1 from 25.
Write this result.
Ex [1] 492 =_________.
a)
The difference from 50 is 1.
b)
12 = 1. Write 01
to take up 2 place values.
c)
25 – 1 = 24. Write 24.
d)
The answer is 2401.
Ex [2] 422 =_________.
a)
The difference from 50 is 8.
b)
82 = 64. Write
64.
c)
25 – 8 = 17. Write 17.
d)
The answer is 1764.
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