Agreed completely with Oxford Blue. Basically all this is asking you is "do you know the earth is an elipse ???". Assuming you do, it then becomes basic maths.
As with a lot of JAA questions, they will phrase them in such a way as to make you think "what the hell is this about" or they will incorporate lots of "big numbers" into the question to make it look daunting.
But when you look at them objectively, you soon realise they are actually not that bad, and it's just the examiner who is trying to phase you with "big numbers" or jargon.
Best get used to this fact, it does happen alot. Once you realise this is all that's going on, you're half way there. Otherwise, you will be trying to "learn" answers until you are blue in the face, and as stated by OB, that is not, nor should it be, feasible.
Good luck.