Question

It takes the pendulum of a clock 7 seconds to strike 4 o’clock. How much time will it take to strike 11 o’clock?

• A. 18 seconds
• B. 20 seconds
• C. 19.25 seconds
• D. 23.33 seconds

Hint:

For clock striking problems, always count the intervals (strikes - 1) and use proportional scaling to find the time for any number of strikes.

Answer 1

The Correct Option is D

When a clock strikes a certain hour $n$, it actually makes $(n - 1)$ intervals between the strikes.
For example: At 4 o’clock, the bell strikes 4 times, but the time measurement is between the first strike and the last strike, which is $(4 - 1) = 3$ intervals.
Given: Time for 3 intervals = 7 seconds.
Thus, time for 1 interval = $\frac{7}{3}$ seconds.
At 11 o’clock, the bell strikes 11 times, which corresponds to $(11 - 1) = 10$ intervals.
Therefore, time taken = $10 \times \frac{7}{3} = \frac{70}{3} \ \text{seconds} \approx 23.33 \ \text{seconds}$.
Hence, the required time is $\boxed{23.33 \ \text{seconds}}$.