The perimeter of a rectangle is defined as,
P = 2(l + w)
P = perimeter
l = length of rectangle
w = width of rectangle.
In our instance,
P = 48 cm
l = 3w
w = w.
Plug our values into the perimeter formula above.
48 cm = 2(3w + w).
Simplify the right side.
48 cm = 2(4w).
Multiply 2 by 4w.
48 cm = 8w.
Divide each side by 8.
6 cm = w.
We know the length is 3 times as much as the width, therefore,
l = 3(6).
Multiply 3 by 6.
l = 18 cm.
The length is 18 cm and the width is 6 cm.