To find the population of the city in 2020, we calculate the growth and decline in two stages:

Step 1: Population growth from 2010 to 2015

The population in 2010 was 231,000, and it grew by 5% from 2010 to 2015.
To calculate the population in 2015: $\text{Population in 2015} = 231,000 \times (1 + 0.05) = 231,000 \times 1.05 = 242,550$

Step 2: Population decline from 2015 to 2020

The population in 2015 was 242,550, and it fell by 3% from 2015 to 2020.
To calculate the population in 2020: $\text{Population in 2020} = 242,550 \times (1 - 0.03) = 242,550 \times 0.97 = 235,273.5$

Step 3: Round to the nearest 100

The population in 2020, rounded to the nearest 100, is: $\boxed{235,300}$

Let me know if you’d like further clarification or details!

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Related Questions:

1. What would the population have been in 2020 if the growth from 2010 to 2015 had been 10% instead of 5%?
2. What is the percentage change in population from 2010 to 2020?
3. If the population continued to decrease by 3% every 5 years after 2020, what would it be in 2030?
4. How long would it take for the population to halve, assuming a constant 3% decline every 5 years?
5. What would the population in 2020 have been if it experienced no changes from 2010?

Tip:

When calculating successive percentage changes, always apply the percentages step-by-step to avoid errors in calculations.