In the middle pond is a patch of moss. The moss doubles in size every day. After exactly 20 days the complete pond will be covered by moss.

After how many days will half of the pond be covered by the moss ?

19 days

why is 19 days , can you explain to me plz ...

To determine how many days it will take for half of the pond to be covered by moss, we need to understand the pattern of growth. According to the problem, the moss doubles in size every day.

Let's use a bit of logic to figure this out:

- On day 1, the moss covers half of the pond because it doubles in size.
- On day 2, the moss doubles in size again, covering the entire pond.

Therefore, we can conclude that it takes 2 days for the moss to cover the entire pond.