This lily pad riddle is the third riddle I found from reading Maria Konnikova.

If you are interested, here is the first.

And here is the second.

Can you get all three?

**Question**

In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of the lake?

**Answer**

We know that the lake is entirely covered on day 48.

So what was it the day before that?

If the lily pad patch doubles every day, the day before day 48, it was covering half the lake.

Right?

If you double half a pie you have a whole pie.

So how long would it take for the lily pad patch to cover half of the lake?

47 days.

Tricky tricky, I know.

I discovered this question in *Mastermind*, By: Maria Konnikova.

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