conversations.from: human
conversations.value: Grace can read a 200-page book in 20 hours. How long would it take her to finish reading a 250-page book at this constant rate?
conversations.from: assistant
conversations.value: Grace can read 200/20 = 10 pages in 1 hour.
  So she can finish a 250-page book in 250/10 = 25 hours.