Human: 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? Assistant: 
How many pages can Grace read in 1 hour? ** Grace can read 200/20 = <<200/20=10>>10 pages in 1 hour.
How many hours would it take Grace to finish a 250-page book? ** So she can finish a 250-page book in 250/10 = <<250/10=25>>25 hours.
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