Find the surface area of the composite figure

SA = 644 cm²

Step-by-step 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

Hope this helps!! :)

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according to the triangle sum theorem, all the angles in a triangle must add up to 180 degrees. if we know one angle is already 90, we do 180-90=90. the other 2 angles must add up to 90, exactly.

step-by-step explanation: