Obvious seems to depend on conditioning. For me the correct answer to the lily pad question seemed completely obvious. On the bat and ball problem, I experienced a cognitive dissonance, the knee jerk answer appeared unbidden, yet something also seemed wrong about it so I stopped to actually think about it before answering correctly. Unconscious algebra would appear to be unreliable for most of us.
My guess would be familiarity with binary numbers and powers-of-two in a computer context (bytes, ints, longs, shift-operations, etc.) helps make the lily-pad answer 'obvious' to some people. Experience in a particular domain can hone a different reflexive intuition from the norm.
This was my experience as well. I was very surprised by both: my inability to accept my knee-jerk (because I knew it was a "trick" question) and b.) the 2 minutes it took me to puzzle out why it was 1.05. Which surprises the hell out of me, as I've had more than my fair share of high level math courses.
