Days for ten growing lily pads to cover a pond

A pond has area $20480$ square feet. Ten lily pads, each $1$ square foot, are placed on it, and each pad doubles in area every day. Assuming pads never overlap, after how many days is the pond fully covered?

$11$ days. Each pad must reach $\tfrac{20480}{10}=2048=2^{11}$ square feet, and after $N$ days a pad has area $2^N$.