Step-by-step explanation:
just take a deep breath, shake your limbs, and then focus on it again.
the surface consists of 5 areas :
front and back triangles (2)
left rectangle
right rectangle
floor rectangle
the area of a rectangle is simple :
length × width
the area of a triangle is
baseline × height / 2
each of the front and back triangles has an area of
5 × 4 / 2 = 5×2 = 10 cm²
both of them have then 10×2 = 20 cm²
the left rectangle is
9×6 = 54 cm²
the right rectangle is
9×5 = 45 cm²
the floor rectangle is also
9×5 = 45 cm²
so, the total surface area is
20 + 54 + 45 + 45 = 164 cm²
