Maths Misconceptions

Good youre sorted now. For this one, if the hole stumped you, just do it without the hole then redo it with the hole. But for a question like this, I think its less about problem solving and more simply about practice as dfranklin suggested. The a level stuff is the differentiation (b) which you seem happy with. The part (a) goes back to old babylonian-egyptian stuff so transforming a field perimeter/area problem into a quadratic. Here its just 1 dimension higher, so transforming an area/volume problem into a cubic.

Hi, just came back to ask for help on another question. I can do parts b and c (once I saw the answer to part a) pretty easily but I don't get how you are supposed to do part a.I get to p.q + p.r but I can't work out how to find the values. The answer is 4.5