Question

A certain 12-hour digital clock displays the hour and the minute of a day. Due to a defect in the clock whenever the digit 1 is supposed to be displayed it displays 7. What fraction of the day will the clock show the correct time?

  (A) 1/2

(B) 5/8

(C) 3/4

(D) 5/6

Answer 1

Correct option  (A) 1/2

Explanation:

The clock will show the incorrect time (between 1 – 2, 10 -11, 11-12 , 12 - 1 day and night both) 

∴ in correct time 8 × 60 = 480 (each minute it will display 1) 

Remaining 20 hours it will show the incorrect time 16 × 15 = 240 

 Total incorrect time = 240 + 480 = 720 

correct time = 1 – incorrect time