I am sitting the F9 exam in September 2016 and am a bit confused by the study books that I have been using being as the discounting of annuities and perpetuities seems inconsistent in that some of the answers to the practice questions have rounded the annuity /perpetuity factor to 3 decimal places whereas on other questions this is not the case so I am hoping to get clarification on what the correct approach is to avoid losing marks.