Final answer:
The annual rate of increase of the population of this city is approximately 6%.
Step-by-step explanation:
The annual rate of increase of the population of this city can be calculated using the rule of 70. The rule of 70 is an estimation used to determine the time it takes for a quantity to double at a constant growth rate. The formula for the rule of 70 is: doubling time = 70 / growth rate.
In this case, the population of the city doubled in 12 years. Therefore, the doubling time is 12 years. Substituting this value into the formula, we get: 12 = 70 / growth rate.
To solve for the growth rate, we can cross multiply and then divide both sides of the equation by 12: growth rate = 70 / 12 = 5.83%
Therefore, the annual rate of increase of the population of this city is approximately 5.83%. Rounded to the nearest whole number, the answer would be 6%. So option B) 6% is the correct answer.