Discount factor calculations – manual.

Hi John, I have just realised after failing the F9 exams twice by 1 mark, I have been using the formula ( 1/1.10^n^) to get the discount factors manually in order to arrive at discounted cashflows which gives me a slightly different answers to the suggested answers. DO you think i would be losing points if the answers are slightly different despite the fact that I used the more efficient way to calculate the discount factor which saves my time from looking at the discount factor tables over and over again?
Also it’s easy and quick to follow this method since I will be doing a CBE exam. Please help!! I am pretty sure this would have been where I lost the marks.