Hi,

I think 93.33% maybe the right answer because the average is being calculated in the scope of the whole year or whatever months (Jan-June) included.

While your expectation of the answer being 97.5 % is wrong because, its just the average of percentages of every month.

Just try to take the average of sales for each individual months (For Ex. sales/30) and then for whole year(sales/365) with some random values.