Answer:
7
Step-by-step explanation: calculate the prime factors of 7 and 21, than find the greatest common factor
The population before the increase was 894.
The key to understanding the question is to keep the details at the fore.
Percentage = 25%
Amount = 230
Our answer to the estimation is given by the formula:
The answer is: 
The explanation for this answer is shown below:
1. By definition, the amount of second required for the pendulum to move from its resting position and return, is the period.
2. As you can see in the graph attached in the exercise, the wave interval is repeating every two units of x (or
).
3. Therefore, the period is
.