Answer:
180
Step-by-step explanation:
Lateral surface area is the area that can be seen from the solid, while total surface area includes the region that can't be seen on the solid. For example in cylinder: LSA = pi*r*l while, TSA = 2pi*r^2 + pi*r*l .
The area of a triangle is given by the formula

, where B is the base and h is the height. We can rearrange this formula to solve for B.

.
We plug in the given area, 640 square millimeters, and the given height, 32 millimeters.

.
40 mm is our final answer.