1. Double the length of the rectangle. For example, the length is 21. Multiplying 21 by 2 results in 42. 2. Subtract the doubled length from the perimeter. For this example, the perimeter
http://www.ehow.com/how_7869620_calculatewidthre...

if you have the length of one side  plus the perimeter. Divide the perimeter by 2, then subtract the known side  this leaves you with the unknown dimension. For example. Say you
http://wiki.answers.com/Q/How_do_you_find_the_widt...

The two formulas needed are P =
http://www.chacha.com/question/howdoyoufindthe...

You can't find the width and length from only the perimeter. 2W + 2L = 54. (W + L) = 27. They could be 26 and 1, or they could be 13 and 14, or they could be 12.345 and 14.655. Are
http://answers.yahoo.com/question/index?qid=201205...
