Final answer:
Using the rule of 70, dividing 70 by the annual growth rate of 6.9%, it will take approximately 10 years for the country's population to double. The correct answer is option b) 10 yr.
Step-by-step explanation:
To calculate how long it will take for the population of a certain country to double with an annual growth rate of 6.9%, we can use the rule of 70. This is a simplified way to estimate the doubling time of a population based on its growth rate. The rule states that you divide 70 by the annual growth rate to get the approximate doubling time in years.
To apply this rule to the given growth rate of 6.9%, the calculation would be:
70 / 6.9 ≈ 10.14
Therefore, rounding to the nearest year, it will take approximately 10 years for the country's population to double.
Given these calculations, the correct answer is (b) 10 years.