Question

A clock strikes once at 1 o'clock, twice at 2 o'clock and so on. If it takes 6 seconds to strike at 3 o'clock, how much time will it take to strike at 9 o'clock?

• A. 24 seconds
• B. 18 seconds
• C. 20 seconds
• D. None of these

Hint:

Count the gaps between strikes, not the strikes themselves; 3 strikes have only 2 gaps.

Answer 1

The Correct Option is A

Step 1: Understand "6 seconds to strike 3 times" really means.
When a clock strikes 3 times, there are only 2 gaps, or intervals, between the strikes: the gap between the 1st and 2nd strike, and the gap between the 2nd and 3rd strike. The clock does not spend time on the strikes themselves, only on the gaps.
Step 2: Find the time for one interval.
2 intervals take 6 seconds, so 1 interval takes 6/2 = 3 seconds.
Step 3: Count the intervals at 9 o'clock.
At 9 o'clock, the clock strikes 9 times, so there are 9 - 1 = 8 intervals between the strikes.
Step 4: Compute the total time.
Total time = 8 intervals x 3 seconds per interval = 24 seconds.
Step 5: Match with the options.
24 seconds corresponds to option (1). Note that simply scaling 6 seconds in proportion to the number of strikes (3 to 9) would incorrectly give 18 seconds, since it ignores that only the gaps between strikes take time, not the strikes themselves.