Question

On June 1, a fast-growing species of algae is accidentally introduced into a lake in a city park. It starts to grow and

cover the surface of the lake in such a way that the area it covers doubles every day. If it continues to grow
unabated, the lake will be totally covered, and the fish in the lake will suffocate. At the rate it is growing, this will
happen on June 30.
a. When will the lake be covered halfway?

Answer 1

June 29

Explanation:

Since the question clearly states that the rate of algae growth is such that the area it covers doubles every day then the inverse is also true, i.e. going back a day the area covered is half.

It can be simply assumed that on the previous date from the day the entire lake was covered, half of the area must have been covered. This means that on the day prior to June 30 the lake was half covered, i.e. June 29