I'm not sure how answers are marked in A level Mathematics exams (if it counts, I'm sitting for the CIE board) but when I am doing practice questions based on a book, sometimes my answer may differ by a few hundredths or tenths (usually the third significant figure). When this happens, I usually assume that my calculation is correct and that the difference simply happens because of a choice I use to use or not use the correct form, not the one rounded off to 3 s.f. Would my marks be affected by these differences in an exam and if they do, when do I know whether I should use the rounded off figure or the exact form?

For instance in the work I've recently done, the question comes in 2 parts, the first is that I need to find the area of the sector and the second is the area of the chord of said sector. What I did was subtract the area of triangle from my previous answer but my answer was off by 2 hundredth. I did the calculation again using the correct form of the sector, not the one rounded to 3 s.f. and got the answer written in the answer booklet.

Would my answer be considered correct?