Question 36562
1) A square piece of paper is folded in half vertically. If the resulting figure has a perimeter of 12 cm, what was the area of the original square? 
Let the square have sides of "s" before the folding.
After the folding the sides are s,s,s/2,s/2
The perimeter of the resulting rectangle is 3s=12 cm.
Then s=4 cm
The area of the original square is 4^2 = 16 cm^2


2) Find the value of the digit A if the 5-digit number 12A3B is divisible by both 4 and 9, and A=/B (The sign between the A and B is actually an equal sign with a slash going through it, not sure what it means). 

If the number is divisible by "9" the sum of the digits is 9 or 18 or 27
or some numtiple of 9.  
If the number is divisible by "4" it must be an even number.

Trying different combinations of digits that meet these criteria you will 
find that A=1 and B=2 is a correct answer.

3) What is the sum of the digits used to form the integers from 45 to 100, inclusive? 
I assume their is some simple way to do this but I do not know what it is.

Cheers,
Stan H.