The first person who saw Greenland told
2 people about it the day he saw it.
The next day, those 2 people each told
2 more people, and the next day, those 4 people each told 2 more
people, and so it went.
the Red was the last person in
Iceland to hear the rumor about Greenland, how many days after
the rumor started did he hear about it? At
that time, Iceland had a population of 20,000.