The Growing Lily Puzzle
Lily is a lilypad in a small pond. Lily doubles her size each day. On the 20th day, she covers the whole pond. On what day was Lily half the size of the pond?
On the 19th day.
Explanation:
Since Lily doubles her size each day, she must have been half the size of the pond the day before she covered the entire pond. Therefore, if the pond is fully covered on the 20th day, it was half-covered on the 19th day.
