Sounds like one of those stupid Common Core “gotcha” questions. How about providing the total square footage of the pond and the average size of a lily pad for us really old farts that like to calculate things by good, old-fashion mathematics?..../s
If the number of lilly pads doubles every day, and the pond will be covered on day 48, then it will be half-covered on day 47. That's what "doubles every day" means. How will the square footage of the pond help you calculate that better?