A rectangle has a perimeter of 22.4mm. If the length is 7.2mm, what is the width ?

To find the width of the rectangle given its perimeter and length, we can use the formula for the perimeter of a rectangle:

\[
P = 2 \times (L + W)
\]

where \( P \) is the perimeter, \( L \) is the length, and \( W \) is the width.

Given that the perimeter \( P = 22.4 \) mm and the length \( L = 7.2 \) mm, we can rearrange the formula to solve for \( W \):

\[
22.4 = 2 \times (7.2 + W)
\]

First, divide both sides by 2:

\[
11.2 = 7.2 + W
\]

Next, subtract 7.2 from both sides to solve for \( W \):

\[
W = 11.2 - 7.2
\]
\[
W = 4 \text{ mm}
\]

Therefore, the width of the rectangle is **4 mm**.