[hadcat]

I did not read past the pond size because you miss calculated.

Doubles in size every day.

1 foot
2 foot
4 foot
8 foot
16 foot
32 foot

The answer is the 5th day the lily pad covers the pond.

Is the other math in the article correct?
This is why I think not.

[Pete]

Is the other math in the article correct?

Actually, I never said the lily pad in the second scenario is 1 square foot. My starting assumption is that it covers the pond in 30 days rather than the size of the lily pad. In math terms, scenario 1 sets the initial condition and solves for t (time). Scenario 2 sets t (time) and solves for the initial condition.

I thought that might be confusing when I wrote it. That is, that the assumption from scenario 1 would implicitly carry over to scenario 2 but I went ahead because I didn't think anyone would do the math even if they erroneously started with the 1 square foot assumption in scenario 2. You did.

I should probably change it to avoid the confusion.

[NJ_Tom]

If you reread, you'll see that in the second instance, the author said said "imagine the same pond with a very small lily pad in the corner."

Back-calculating, he finds the original lily pad to have been 1/10 of a square inch. The math is perfectly correct.