Question

The pond lilies in a certain pond grow at a rate such each day they cover twice as much of the pond as they did the day before. The pond is of a size that will be completely covered at the end of 30 days. On what day will the pond be 1/10th covered?

Answer 1

1/10th means 10%

30th day - fully covered -------------------------- (100%)
29th day - half covered -------------------------- (50%)
28th day - one-fourth covered (half of half) ---------- (25%)
27th day - one-eighth covered (half of one-fourth) ---- (12.5%)
26th day - one-sixteenth covered (half of one-eighth) -- (6.25%)

so 10% i.e. 1/10th will be covered in 27 days !!