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[copper cape]

Calculate the surface area of the new solid by calculating (6*6)18=648
The 2x2 cuboid had a surface area of 576, so you want to find the percentage increase from 576 to 648
648100/576=112.5
112.5-100=12.5
12.5% increase

[limber quiver]

I know I got it right but how is the old one 576 again

And how you work out the SA of the new one

[copper cape]

You add up the area of each face that is exposed to get the surface area

For the first solid there are 4 faces at the top, 4 at the bottom, and a total of 8 on the sides

That gives a total of 16 faces, each face has an area of 36 because it’s a square with side length 6

36*16=576

That’s the old one

To work out the new one it’s the same method so you count up the exposed faces