Question 139542
The perimeter of a square is just the sum of the lengths of the sides.  Since the sides of a square are all the same length, you can just divide the perimeter by 4 to get the length of one side.


The diagonal of a square makes an isoceles right triangle with two of the sides, and the sides of an isoceles right triangle are in proportion 1:1:{{{sqrt(2)}}}.


So once you have discovered the length of one of the sides, multiply that value by {{{sqrt(2)}}}.


Depending on whether the question asks for an exact answer or a decimal approximation, either leave the answer in terms of the radical or use your calculator to calculate the approximate value to the level of precision indicated.  If it doesn't specify, assume that you are required to provide the exact answer.  If it specifies a decimal approximation but does not specify the precision, round to the nearest whole centimeter -- because your perimeter measurement is given to the nearest whole centimeter.