square mirror

If the side of the mirror is A Inches then the length of the diagonal is A*√2 Inches.
A√2 = 20
A = 10*√2 = 14.14
Perimeter of the mirror = 4A = 4*14.14 = ~57 = ~60.

grandh01 wrote:If a square mirror has a 20-inch
diagonal, what is the approximate
perimeter of the mirror, in inches?
(A) 40
(B) 60
(C) 80
(D) 100
(E) l20

For this question it's important to remember three things:
1) The diagonal of a square is equal to x√2 when x=side of the square
2) √2 is approximately 1.41
3) The premier of a square is equal to 4x, when x=side of the square.
OK now, lets solve this thing:
So the diagonal is x√2= x*1.41 This is equal to 20. x*1.41 = 20
solve for x you get x=14 (plus some remainder, but this is an approximation question so I don't care about the remainder).
Now 14*4=56 (plus some remainder which would have been multiplied by 4, so obviously our answer is larger than 56)
The closest answer is 60. Choose B