a gardener places lilies in a pond.He does on the first day of the month of september.it double in volume every day until the last day of the month,the pool is full.On what day of the month was the pool half full of lilies?

It will be half full of lilies in the second to the last day of the month.

is it day 20,or day 15

Neither.

It's half full on September 29.

Remember the lilies double every day.

It will be the last day....

Remember Ms. Sue, Friday, March 1, 2013 at 9:22pm "Remember the lilies double every day" So the previous day would be half the amount.

To determine the day of the month when the pool was half full of lilies, we can work backwards from the last day of the month and calculate the volume of the pool at each day.

Let's assume that on the last day of September, the pool is full and has a volume of 100%. On the day before the last day, the pool would have been half full, at 50% volume.

Since the lilies double in volume every day, we can conclude that on the day before the last day, the pool was at 50% volume. Therefore, the pool was half full of lilies on the second-to-last day of September.