At 6'o clock, the clock ticks(strike) 6 times. The time between first and last ticks was 30 sec.

Q: At 6’o clock, the clock ticks(strike) 6 times. The time between first and last ticks was 30 sec. How much time it takes at 12’o clock?
i) 24
ii) 33
iii) 66
iv) 96

Answer:  66

At 6’o clock ticks 6 times
for first strike there is no time needed.
so 5 interval is there.
time between first and last tick is 30 sec.
so
30/5=6
i.e time of each interval is 6 sec.

Similarly at 12’o clock, clock ticks 12 times i.e 11 interval (for first strike there is no time needed.)
so
1 interval time=6
so 11 interval=11*6=66

It will takes 66 sec at 12’o clock.