The diagram shows the dimensions of a wooden block. the block will be covered with a reflective film. how much of the film is needed to cover the entire block?

This questions is asking for the Surface Area of the wooden block. To find Surface Area, you have to add up the area of every surface on the block: the two triangles on each end, the side, the bottom, and the angled top.

Triangles:
The area of a triangle is found with , where b = base and h = height. For these triangles, the base is 3 and the height is 4, so you plug it in to get:

However, there are two triangles with that area, so the total area is 6 x 2 = 12

Bottom:
The bottom has a length of 6 and a width of 3, so the area is 6 x 3 = 18

Side:
The side has a length of 6 and a height of 4, so the area is 6 x 4 = 24

Angled Side:
The angled side/top has a length of 6 and a width of 5 (remember, it's diagonal), so the area is 6 x 5 = 30.

Add up all of the areas to get 12 + 18 + 24 + 30 = 84 cm^2, or answer choice B.