Step-by-step explanation:
this consists of 5 sides
top and bottom (equal)
left
right
front
the total surface area is the sum of all 5 areas.
the area of a rectangle is
length × width
the area of a triangle is
baseline × height / 2
in our case we have
top and bottom : 10×4/2 × 2 = 10×4 = 40 cm²
left : 8×9 = 72 cm²
right : 5×9 = 45 cm²
front : 10×9 = 90 cm²
the total surface area is
40 + 72 + 45 + 90 = 247 cm²
