I think the options you presented are all too big to be the median. 3.1 is a possible median.

Assume already known all the rainfalls for each month, put the 12 numbers in ascending order, Several key characters appear for the 2nd to the 11th number
1. sum of the 6th and 7th number = 2*median
2. 2.2<= 2nd-5th number<=6th number
7th number<= 8th-10th number<=12.2

Then just simply test each one of the answers and see if they can make both above condition true

Details pls see attached calc

this was a real test question on the test and i was pretty sure the numbers for a,b,d,e are correct. i was stumped and guessed 3.2

The way I think is if you take mean of highest & lowest number it is 7.2.
And since the mean is 3.5, definately the data is skewed toward lowest value which brings the mean down. This is possible only when the median of data must be less than 3.5
Answer = 3.2

I go with gmatplaye's explanation..... it has to be less that 3.5...and only option is A.