Keeping the Brain Cells Active

[ezdays]

I have to agree with Charlie, if it cover fully in 30 days after doubling, it was half that the day before. We're just not sure what time that happened though

Well in this case I took the obvious route when the correct answer is I believe 28 days. I'm too old for this stuff.

Duuno, if it was half covered in 28 days and doubled in size, it would be fully covered in 29 and spilling over at 30 days. Unless, of course, there is a twist that I missed, then anything is possible. :?