Answer is : (a) 1/2
Digit 1 appears in 1, 10, 11, and 12 in hour.
∴ The clock will show the incorrect time between 1-2, 10-11, 11-12, 12-1 day and night both incorrect time (8 x 60) = 480 min
Digit l appear in minutes 1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 31, 41, 51 = 15 min
∴ It will shows the incorrect time = 16 x 15 = 240 min
Total incorrect time = 240+480 = 720 min
Correct time = 24 x 60 - 720
Fraction of correction time