If you “unfold” the wrapping paper around this triangular prism, you have
2 triangles
Base 40, to find the height(dotted perpendicular line segment)
a^2 + b^2 = c^2. ... 20^2+ b^2 = 29^2 … 400+ b^2 = 841
- 400. -400
b^2 = 441 … b=21 this is height
1/2(40)(21) = 420 + 420
3 rectangles
Two are 70x29 = 2030 +2030
One is 70x40 = 2800
Add all 5 numbers:
420
420
2030
2030
+ 2800
7700