Question 1172906
Rectangles A and B are both four times as long as they are wide
 and the length of rectangle A is three times the length of rectangle B.
 If the difference in the perimeters is 16cm, find the dimensions of each rectangle.
:

let w = width of rectangle B
then
4w = the length of rectangle B
And
3(4w) = 12w = the length of rectangle A
3w = the width of rectangle A, (1/4th of A's length)
:
2(12w + 3w) - 2(4w + w) = 16
simplify, divide equation by 2
(12w + 3w) - (4w+w) = 8
15w - 5w = 8
10w = 8
w = 8/10
w = .8 cm is the width of rectangle B
and
4(.8) = 3.2 cm is length of rectangle B
then
3(.8) = 2.4 cm is width of rectangle A
and
4(2.4) = 9.6 is length of rectangle B
:
:
see if this checks out
2(9.6 + 2.4) - 2(3.2 + .8) = 
2(12) - 2(4) = 
24 - 8 = 16