6)Simplify $\displaystyle (3g)^3$ I couldn't think of an answer for this apart from maybe changing the 3 at the start as because it's 3gx3gx3g so 27g^3?

7)A square has a semicircle cut out of it. Calculate the perimeter of the shape correct to 3dp. (sides of 12cm)

Here I got 54.85 which can't be correct because it says caluclate to 3dp. I did the perimeter as perim=piexdiameter. (then halving this to get semi circle etc etc)