The city’s population has grown by \(\frac{\mathrm{1} }{\mathrm{6}} \) in 2020, and in 2021 it has grown by another \(\frac{\mathrm{2} }{\mathrm{5}} \) from 2020. If in 2019 the population was 155,880 people, what has it become in 2021?

Step 1: Determine the population growth in 2020.
We need to find what is \(\frac{{1} }{{6}} \) of 155,880. This is the population growth in 2020. The key words “has grown by \(\frac{{1} }{{6}} \)” point to multiplication.
\(155,880×(\frac{{1} }{{6}} \)) = (\(\frac{{155,880} }{{1}} \)) × (\(\frac{{1} }{{6}} \))
= (155,880 × 1)/(1 × 6)
= (155,880)/6
= 155,880 ÷ 6
= 25,980
Step 2: Find the total population in 2020.
The total population in 2020 is the population in 2019 plus the population growth in 2020.
155,880 + 25,980 = 181,860
Step 3: Determine the population growth in 2021.
We need to find what is 2/5 of 181,860. Again, we find the keywords “has grown by 2/5” to be sure that we should use multiplication.
\(181,860 × (\frac{{2} }{{5}} \)) = (\(\frac{{181,860} }{{1}} \)) × (\(\frac{{2} }{{5}} \))
= (181,860 × 2)/(1 × 5)
= (363,720/5)
= 363,720 ÷ 5
= 72,744
Step 4: Find the total population in 2021.
The total population in 2021 is the population in 2020 plus the population growth in 2021.
181,860 + 72,744 = 254,604
The city’s population in 2021 is 254,604 people.