A = l x w
Since
l = 3w
Substitute the l with 3w
The formula will be
A = 3w + w
A = 4w
An example:
The
given known values are: Length of 4 cm Width is unknown Perimeter is 34
cm Find the dimensions of the rectangle. Since the geometric formula
for perimeter is:
P= 2 (l + w)
L = 2w – 4 cm
W =?
Derivation and solution:
34 = 2 (2w - 4) + 2w
34 = 4w – 8 + 2w
42 = 6w 42/6 = w
W = 7 cm
34 = 2l + 2(7)
34 = 2l + 14
2l = 34 – 14
2l = 20
L = 20/2
L = 10 cm
