It doubles every day, so the day before it covers the whole lake, it covers half of it. The answer that jumps out is 24.
A patch of lily pads on a lake doubles in size every day. It takes 48 days to cover the whole lake. How long does it take to cover half the lake?
Give me a hintThe hint
Work backwards from day 48.
Reveal the answerHide the answer
47 days
Source: Shane Frederick, Cognitive Reflection and Decision Making, Journal of Economic Perspectives, 2005