Question 191499: A digital clock displays the hour and minute of a day. Unfortunately, whenever it is supposed to display a 1, it mistakenly displays a 9. What fraction of the day will the clock show the correct time?
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! A digital clock displays the hour and minute of a day.
Unfortunately, whenever it is supposed to display a 1, it mistakenly displays a 9.
What fraction of the day will the clock show the correct time?
;
Find the no of minutes that it will display the incorrect time:
Total min in 12 hrs. 12 * 60 = 720 minutes
:
The hrs that use 1: 01, 10, 11, 12, wrong for 4 hrs, 4 * 60 = 240 minutes
:
the minutes digits that will be wrong for each hr:
01, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 31, 41, 51. Total of 15 min each hr
:
4 hrs are completely wrong,
the remaining 8 hrs are only wrong for 15 min each; 8 * 15 = 120 min
:
Total wrong minutes, 240 + 120 = 360 min.
 =  the time it is correct.
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