This revision aid for L1/L2 (mainly L2) Pearson Edexcel Functional Skills maths gives a side-by-side comparison of perimeter, area and volume, the sort of units that would be involved with each and a worked Functional Skills example of each with a PAV mnemonic for remembering which is which. I have also looked through the last few years of Pearson Edexcel FS for the sorts of questions that require each one.