16.
At what time, in minutes, between 3 o'clock and 4 o'clock, both the needles will coincide each other?

17.
How many times do the hands of a clock coincide in a day?

18.
How many times in a day, the hands of a clock are straight?

19.
A watch which gains uniformly is 2 minutes low at noon on Monday and is 4 min. 48 sec fast at 2 p.m. on the following Monday. When was it correct?

20.
A watch becomes fast by 5 minutes everyday. By what percent does it become fast ?