I am learning this right now but in two hours I will tell you
Odd numbers take the form 
, where 
is an integer. When 
, the last odd number would be 799. So we're adding
By reversing the order of terms, we have
and we can pair up terms in both sums at the same position to write
so that we are basically adding 400 copies of 800, and from there we can find the value of the sum right away:
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We could also make use of the formulas,
We have
The area is A. 84 square inches
Question 2. :
8^2 = 64 and 9^2 = 81, therefore the square root of 65 falls between these two values, 8 and 9, 64<65<81
Question 3. :
13^2 = 169 and 14^2 = 196, the correct answer is square root of 175, because 169<175<196
Hope this helps, you only need to know the squared values and square roots.
