The area of a triangle is given by the formula [tex]A= \frac{1}{2}Bh[/tex], where B is the base and h is the height. We can rearrange this formula to solve for B.
[tex] \dfrac{A}{ \frac{1}{2}h} = B\\ \\\\\dfrac{2A}{h} = B[/tex].
We plug in the given area, 640 square millimeters, and the given height, 32 millimeters.
[tex]B= \dfrac{2(640)\ mm^2}{32 \ mm} = 40 \ mm[/tex].
40 mm is our final answer.