Writing formulas in essay questions


For the essay questions, do we need to write formulas before doing the calculation? I find it much more efficient to jump directly into the calculation (ie. Bond duration adjustments or beta calcs or h-model) but I am wondering if writing formulas is required before that? Do you guys usually write formulas before to get part marks in case calc is screwed up?

Do you also explain the logic behind buying or selling x number of futures contracts if the question just states to calculate how many futures to sell?

Some question about formulas. Someone?