Step-by-step explanation:
as the graphic shows, there are 2 objects : 1 block and 1 triangular shaped half-block.
the block is
7cm × 6cm × 2cm
the half-block is
8cm × 7cm × 6cm
with 10cm being the length of the tilted "roof" area.
the 2 sides facing each other are not visible to the observer, so, they are not part of the surface area of the composite figure.
let's start with the block :
top and bottom 7×2
front and back 6×2
no left (fully covered by the half-block)
right 6×7
that gives us :
2 × 7×2 = 2×14 = 28 cm²
2 × 6×2 = 2×12 = 24 cm²
6×7 = 42 cm²
in total : 94 cm²
the half-block :
top 10×7
bottom 8×7
front and back (triangles) 8×6/2
no left (due to being a half-block)
no right (fully covered by the block)
that gives us :
10×7 = 70 cm²
8×7 = 56 cm²
2 × 8×6/2 = 2×24 = 48 cm²
in total : 174 cm²
so, the complete surface area of the composite figure is
94 + 174 = 268 cm²
