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? Think carefully first, then make a decision:
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Grace can read 200 / 20 = 10 pages in 1 hour. So she can finish a 250 - page book in 250 / 10 = 25 hours. So, the answer is 25.
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