I disagree. If it takes 48 days to cover the lake, and the lilly pads double every day, then 1/2 of the lake is covered on day 47, 1/4 on day 46, 1/8 on day 45, etc.
How do you get 1 day as an answer to the question "how long would it take for the patch to cover half the lake?"
If it’s half covered on day 47, then it just takes one day to cover the remaining half.
47 days covered the first half and one more covered the second half.
Because the last day, it covers half the lake. So it took one day to cover half the lake.
It was 50% covered, and in one day, the other 50% was covered.
They didn’t say which half. if you go from zero coverage, it takes 47 days to cover half the lake. The last day’s growth also covers half the lake.
On day 48 a full half of the lake is covered.
On Day 47, lake was half covered.
On Day 48, lake was entire covered.
Therefore, it took only one day (singular “day”) to cover the lake (going from Day 47 to Day 48).
It took 47 days (plural “days”) to cover half of the lake.
Pretty perceptive by SAM! He is exactly right about the ambiguous wording.
The lake is half covered on day 47. Then fully covered on day 48.
The question neglected to state they were looking for the time to go from completely uncovered to half covered.