During the five year period from 2018 to 2022, the populations of Countries A, B, and C showed
consistent growth. The total population of the three countries in 2018 was 100 million whereas in 2021
and 2022 it was 20% and 30% more than that in 2018. The ratio of the populations of countries B and
C in 2022 was 4 : 3.
Country A: In 2018 the population was 50 million. In 2019 and 2021 the population was respectively
4% and 12% more than that in 2018 whereas the population in 2020 was the average of that in the
years immediately before and after it. The ratio of the population in 2018 and 2022 respectively was 5
: 6.
Country B: In 2018 the population was 60% that of Country A. It increased by 10% in 2019 with
respect to the previous year whereas the increase in numbers in 2020 was the same as that in 2019.
Country C: In 2019 the population increased by 10% with respect to the previous year. In 2021 the
population of C was half that of A in the same year. In the year 2020, the ratio of the populations of B
and C was 3 : 2 respectively

We need to break down the given information systematically and solve for the populations of countries A, B, and C over the years from 2018 to 2022.

### Step 1: Population of Country A

- In 2018, the population of A was 50 million.
- In 2019, the population increased by 4%, so the population of A in 2019 was:
  \[
  A_{2019} = 50 \times (1 + 0.04) = 52 \text{ million}.
  \]
- In 2020, the population of A was the average of the populations in 2019 and 2021:
  - Population in 2021 was 12% more than in 2018:
    \[
    A_{2021} = 50 \times (1 + 0.12) = 56 \text{ million}.
    \]
  - Therefore, the population in 2020 is:
    \[
    A_{2020} = \frac{A_{2019} + A_{2021}}{2} = \frac{52 + 56}{2} = 54 \text{ million}.
    \]
- The ratio of the population in 2018 and 2022 is 5:6. So, the population in 2022 is:
  \[
  A_{2022} = \frac{6}{5} \times 50 = 60 \text{ million}.
  \]

### Step 2: Population of Country B

- In 2018, the population of B was 60% that of A. So, the population of B in 2018 is:
  \[
  B_{2018} = 50 \times 0.60 = 30 \text{ million}.
  \]
- In 2019, the population of B increased by 10%, so:
  \[
  B_{2019} = 30 \times (1 + 0.10) = 33 \text{ million}.
  \]
- In 2020, the increase in population was the same as the increase in 2019, which was 3 million (33 - 30). So, the population in 2020 is:
  \[
  B_{2020

During the five-year period from 2018 to 2022, the populations of Countries A, B, and C showed consistent growth. The total population of the three countries in 2018 was 100 million whereas in 2021 and 2022 it was 20% and 30% more than that in 2018. The ratio of the populations of countries B and C in 2022 was 4 : 3. Country A: In 2018 the population was 50 million. In 2019 and 2021 the population was respectively 4% and 12% more than that in 2018 whereas the population in 2020 was the average of that in the years immediately before and after it. The ratio of the population in 2018 and 2022 respectively was 5 : 6. Country B: In 2018 the population was 60% that of Country A. It increased by 10% in 2019 with respect to the previous year whereas the increase in numbers in 2020 was the same as that in 2019. Country C: In 2019 the population increased by 10% with respect to the previous year. In 2021 the population of C was half that of A in the same year. In the year 2020, the ratio of the populations of B and C was 3 : 2 respectively.

Analyze population growth of Countries A, B, and C between 2018 and 2022. Learn to calculate percentage increases, ratios, and averages to solve population-related math problems. This detailed solution involves population growth trends, suitable for students in Grades 8-10.

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