The length of a rectangle is three times its width.
If the perimeter of the rectangle is $72 \mathrm{~cm}$, find its length and width.
length:
$\mathrm{cm}$
width:
$\mathrm{cm}$

Step 1 ：The problem states that the length of a rectangle is three times its width. We can express this as \(length = 3 \times width\).

Step 2 ：We are also given that the perimeter of the rectangle is 72 cm. The formula for the perimeter of a rectangle is \(2 \times (length + width)\).

Step 3 ：Substituting the expression for length from step 1 into the perimeter formula, we get \(2 \times (3 \times width + width) = 72\).

Step 4 ：Solving this equation for width, we find that \(width = 9 cm\).

Step 5 ：Substituting \(width = 9 cm\) back into the expression for length, we find that \(length = 3 \times 9 cm = 27 cm\).

Step 6 ：Final Answer: The width of the rectangle is \(\boxed{9 cm}\) and the length of the rectangle is \(\boxed{27 cm}\).