So the formula I use is S = L + 2B
Surface Area = Lateral Area + 2(Base)
In this case, it would be
Surface Area = Lateral Area + Base, since there is only one base
L= Perimeter(height)
L= 4(3 times 5)
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2
L= 4(15)
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2
L =60/2
L=30
S= 30 + B
B = 3 times 3 = 9
S= 39
