Sarah is checking out books from the library to read on vacation. She can read 40 words per minute. The books she is checking out have 100 words per page and are 80 pages long. She will be reading for 20 hours. How many books should she check out? Let's think first. Chain of thought:
Each book has 8,000 words because 100 x 80 = 8,000. She can finish each book in 200 minutes because 8,000 / 40 = 200. She will be reading for 1,200 minutes because 20 x 60 = 1,200. She needs to check out 6 books because 1,200 / 200 = 6.
Therefore, the answer is 6.