Question: Peter and Kristin are to read 20 fantasy novels each in a week. Peter can read three times as fast as Kristin. If Peter reads one book in 18 hours, how long will Kristin read half of her books?
Solution:
Since Peter reads three times as fast as Kristin, Kristin will take 18*3 = 54 hours to read one book.
Kristin reads half of her books, a total of 20/2 = 10 books.
The time Kristin will take to read half of her books is 10*54 = 540
Answer: 540