133
Question
Find the squares of the following numbers:
(1) 85
(1) 85
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Solution
The square of any number ending with 5 can be written as:
(a5)2 = [a × (a + 1) × 100] + 25
Here, a is the number excluding the units digit.
So, the square of 85 can be calculated as:
[8 × (8 + 1) × 100] + 25
= [8 × 9 × 100] + 25
= 7200 + 25
= 7225
(a5)2 = [a × (a + 1) × 100] + 25
Here, a is the number excluding the units digit.
So, the square of 85 can be calculated as:
[8 × (8 + 1) × 100] + 25
= [8 × 9 × 100] + 25
= 7200 + 25
= 7225
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