The correct answer is : 340 cm^2
Explain
Trapezium area
1/2h (a+b)
Base area = 1/2h (a+b)
Base area = 1/2(3)(8+12)
As 20/2 = 10
Base area = 3(10)
Base area = 30 cm^2
Use perimeter: 28
Base Area = 30
Height = 10
Surface area = 2(30)+28(10)
Surface area= 60+ 280
Surface are = 340
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