Answer: SA = 644 cm²
Explanation:
STEP ONE: Find the surface area of the smaller rectangle (green)
There are in total 5 sides because one of the sides is not shown on the surface level.
Upper base = 3 × 3 = 9 cm²
4 sides = 3 × 8 × 4 = 96 cm²
Total = 9 + 96 = 105 cm²
STEP TWO: Find the surface area of the larger rectangle (orange)
There are in total 5 whole sides with one side covered by the base of the smaller rectangle (green) which should later be subtracted.
Front and back = 7 × 10 × 2 = 140 cm²
Left and right = 7 × 12 × 2 = 168 cm²
Lower base = 10 × 12 = 120 cm²
Upper base = 10 × 12 - 3 × 3 = 111 cm²
Total = 140 + 168 + 120 + 111 = 539 cm²
STEP THREE: Find the total surface area
SA = Green + Orange = 105 + 539 = 644 cm²
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