Worked example
A town starts with 1,000 people. There are 30 births and 10 deaths, with no migration. What is the ending population?
Answer & why
Answer: 1,020
1,000 + 30 − 10 = 1,020.
Grade 8 · Social studies
Account for population change
Calculate change in an invented population from births, deaths and migration without treating all growth as one cause.
6 authored questions + worked example
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All questions
All 6 authored questions for this skill.
Question 1
A population starts at 2,000; births are 40, deaths 30, arrivals 20 and departures 50. What is the ending population?
- 2,020
- 2,000
- 1,980
- 2,140
A hint
Start population + births − deaths + arrivals − departures gives the ending population in this model.
Answer & why
Answer: 1,980
2,000 + 40 − 30 + 20 − 50 = 1,980.
Question 2
A town has 60 births and 75 deaths in a year. What is its natural population change before migration?
- +15 people
- −135 people
- +135 people
- −15 people
A hint
Start population + births − deaths + arrivals − departures gives the ending population in this model.
Answer & why
Answer: −15 people
Natural change is births minus deaths: 60 − 75 = −15.
Question 3
A town's total population rises by 20. Natural change is +5. In this model, what must net migration be?
- +5 people
- +15 people
- −15 people
- +25 people
A hint
Start population + births − deaths + arrivals − departures gives the ending population in this model.
Answer & why
Answer: +15 people
The two components sum to total change, so 20 − 5 = +15.
Question 4
A report gives only the ending population, not births, deaths or migration. What can it NOT determine by itself?
- The reported ending count.
- Whether an ending count was printed.
- The unit in which the count is stated.
- How much each flow contributed to the change.
A hint
Start population + births − deaths + arrivals − departures gives the ending population in this model.
Answer & why
Answer: How much each flow contributed to the change.
An endpoint alone does not separate the different sources of population change.
Question 5
A town starts with 1,000 people. There are 30 births and 10 deaths, with no migration. What is the ending population?
- 1,020
- 1,040
- 980
- 1,030
A hint
Start population + births − deaths + arrivals − departures gives the ending population in this model.
Answer & why
Answer: 1,020
1,000 + 30 − 10 = 1,020.
Question 6
During a year, 80 people arrive and 50 leave. What is net migration?
- +30 people
- −30 people
- 0 people
- +130 people
A hint
Start population + births − deaths + arrivals − departures gives the ending population in this model.
Answer & why
Answer: +30 people
Arrivals minus departures gives 80 − 50 = +30.