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?
Grace can read 200/20 = 
<gadget id="calculator">200/20</gadget>
<output>10</output>
10 pages in 1 hour.
So she can finish a 250-page book in 250/10 = 
<gadget id="calculator">250/10</gadget>
<output>25</output>
25 hours.

<result>25</result>