Jack's famous beanstalk doubled its height every day After twenty-one days it was as high as the town hall.?

Question

Jack's famous beanstalk doubled its height every day. After twenty-one days it was as high as the town hall. After how many days was it half the height of the town hall?

Answer 1

Wouldn't it just be 21 divided by 2?

which is 10.5, so about 11 days??? :S

Answer 2

Answer: Obviously on the twentieth (20th) day.

Answer 3

20 days

Since it doubles its height every day, the answer would be 20 days, since the next day it would be as high as the townhall.

Answer 4

20 days, certainly.

However, the real question is how high is that town hall?

If the beanstalk on the first day was 1cm tall, it would be 5242.88 meters tall on the 20th day or 17201 feet tall... (3.26miles)... that is one tall town hall!