A watch which gains uniformly, is 5 min slow at 7 o'clock in the morning on Sunday and it is 5 min 48 s fast at 7 pm on following Sunday. Which day was it correct?

Time from 7 am on Sunday to 7 pm on following Sunday
= 7 days 12 h = 180 h
∴ Watch gains (5 + 5⁴/₅) min or 54/5 in 180 h.
Now, 54/5 min are gained in 180 h.
∴ 5 min gained in (180 x 5/54 x 5) h = 83 h 20 min.
= 3 days 11 h and 20 min
∴ Watch is correct after 3 days 11 h and 20 min after 7 am of Sunday.
∴ It will be correct at 20 min past 6 pm on Wednesday.