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2009 AMC 12B Question 10

AMC12 · 2009 AMC 12B

Question 10

A particular $12$-hour digital clock displays the hour and minute of a day. Unfortunately, whenever it is supposed to display a $1,$ it mistakenly displays a $9.$ For example, when it is $1{:}16$ pm the clock incorrectly shows $9{:}96$ pm. What fraction of the day will the clock show the correct time?
  1. $\dfrac{1}{2}$
  2. $\dfrac{5}{8}$
  3. $\dfrac{3}{4}$
  4. $\dfrac{5}{6}$
  5. $\dfrac{9}{10}$