The perimeter of a square newspaper ad is 40 centimeters. how long is each side?

The answer is:  "10 cm" .

Method 1)

2L + 2w = 40 ;  Since the formula for perimeter of a rectangle (Note: a square is a rectangle) is:

                         P = 2L + 2w ;  Note:  L = length; w = width; P = perimeter;

 Factor out a "2":

" 2L + 2w = 40" ;

2 (L+ w) = 40;

Divide each side of the question by "2" ;

         [2 (L + w)] / 2  = 40 / 2 ;

 to get:  (L + w) = 20 ;

Note:  this "rectangle is a square" ; so L= w".

20 /2 = 10 ;

L + w = 10 + 10 = 20.

This is a square, so each side of the square is the same length.

Each side is:  10 cm .

Method 2)


We are given: The perimeter (sum of the lengths of all sides) of a square is "40 cm."  Since a square has 4 sides of equal length:
     Each side is:  40 cm / 4 = 10 cm.

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table