Population Growth

Correct answer: A. The population base has become much larger

The number of people added is an absolute increase, while a growth rate is a percentage of the population base. A lower rate can still produce a similar number of people if it is applied to a much larger population. Therefore, the most appropriate explanation is that the population base has become much larger, which is choice A.

For example, 2 percent of 50 million is 1 million, and 1 percent of 100 million is also 1 million. The rate has fallen by half, but the larger base keeps the absolute addition the same. In general, \(\text{absolute increase}=\text{rate}\times\text{population base}\). Rates and numbers are therefore not identical, and death rate still matters when calculating natural increase. The situation is mathematically possible.

Correct answer: B. Country growing at 1.6 percent

The Rule of 70 estimates doubling time by dividing 70 by the annual growth rate in percent. This shows an inverse relationship: when the growth rate becomes twice as large, the approximate doubling time becomes half as long. The country growing at 0.8 percent takes about 70 ÷ 0.8 = 87.5 years to double.

For the country growing at 1.6 percent, the time is 70 ÷ 1.6 = 43.75 years. This is exactly half of 87.5 years because 1.6 is twice 0.8. Therefore, option B, the country growing at 1.6 percent, is correct. The comparison does not depend only on birth rate; the stated growth rate may reflect the relevant overall population change, including other components where appropriate.

Correct answer: A. 0.8 percent

Growth rate expresses the increase as a percentage of the original population. The country has 150 million people and gains 1.2 million in one year. Therefore, divide the numerical increase by the starting population and multiply by 100. The two quantities must be written in the same unit before calculating, although million can be used directly because it appears in both values.

Growth rate = (1.2 ÷ 150) × 100 = 0.8 percent. Equivalently, 1,200,000 ÷ 150,000,000 × 100 gives 0.8 percent. Thus, option A is correct. The figure 1.2 million is the number of additional people, not the percentage rate. An 8 percent increase would mean 12 million additional people, which is ten times the stated increase.

Correct answer: A. Positive net migration

Natural increase measures the effect of births and deaths only. If it is zero, births and deaths balance each other, so they do not change the population overall. Any remaining change in the total population must therefore come from migration. A positive total growth requires positive net migration, meaning arrivals exceed departures.

The total growth is 1.1 percent and natural increase is 0. Using total growth = natural increase + net migration gives \(1.1=0+\text{net migration}\). Thus net migration is positive 1.1 percent. The correct source is positive net migration, not excess deaths or the birth-death difference, because both are already represented by natural increase. Option A is correct.

Correct answer: B. Positive 0.6 percent

The total growth rate is obtained by adding natural increase and net migration. Here total growth is zero, while natural increase is negative 0.6 percent. The negative natural rate means that deaths exceed births by 0.6 percent of the relevant population. For the final total to remain unchanged, migration must provide an equal positive offset.

Write the relationship as 0 = −0.6 + net migration. Adding 0.6 to both sides gives net migration = +0.6 percent. Therefore, option B is correct. This positive value means immigration exceeds emigration by 0.6 percent, exactly balancing the natural decrease. A negative migration rate would make the population fall further, while zero migration would leave total growth at negative 0.6 percent.

Correct answer: A. Birth rates have declined in recent years

Population is made up of different age groups, and these groups do not all change at the same time. The number of school-age children mainly reflects births in the years before those children enter school. If birth rates decline for several years, younger age groups become smaller. Meanwhile, adults and older people may still keep the total population growing slowly.

Thus declining birth rates are the most likely explanation, so option A is correct. A zero death rate is unrealistic and would not specifically explain fewer children. Total population growth is not the same as growth in every age group, so option C does not follow. Net migration also cannot be assumed to be zero from the information given.

Correct answer: B. Growth rate will face downward pressure from both factors

Total population growth is influenced by natural increase and net migration. Natural increase equals births minus deaths. If the birth rate falls while the death rate stays stable, the gap between births and deaths becomes smaller, so natural increase tends to decline. At the same time, negative net migration means more people leave than enter, which further reduces total population growth. Therefore, choice B is correct.

The relationship can be written as \(\text{total change}=\text{births}-\text{deaths}+\text{net migration}\). A falling birth rate lowers the first part, while a negative migration value lowers the total again. The exact final rate cannot be calculated without more figures, so the answer should describe downward pressure rather than claim certain decline. Choices A and C ignore one or both effects, and D reverses the natural-increase effect.

Correct answer: C. By the combined effect of higher natural increase and negative migration

Population change has two major components: natural increase and net migration. Natural increase equals births minus deaths. If the death rate falls while the birth rate stays unchanged, the gap between births and deaths generally becomes larger, so natural increase rises. Emigration is movement out of the country and makes net migration more negative.

The total growth outcome is found by combining these effects: natural increase plus net migration. Higher natural increase pushes population upward, while heavy emigration pushes it downward. The final result could be faster growth, slower growth, no change, or decline depending on the sizes of both effects. Therefore option C is correct; it is not possible to say that total growth will always accelerate.

Correct answer: A. Gradual fading of population momentum

Population momentum is the continued growth that can occur after fertility has already fallen, usually because a large young population is entering or moving through childbearing ages. This growth does not require a sudden rise in birth rate. It gradually weakens as the age structure changes and smaller generations replace larger ones.

Thus, a country may have low birth rates while total births remain substantial for some years because many young adults are present. Later, as the population structure becomes older and the number of potential parents changes, growth slows and the population can stabilise. This sequence illustrates the gradual fading of population momentum, so option A is correct. It does not show zero deaths or a permanent population explosion.

Correct answer: A. The first rate is 10 percent and the second is also 10 percent

Growth rate is calculated relative to the population at the beginning of each interval. During the first interval, the population rises from 100 million to 110 million, an increase of 10 million. Relative to 100 million, this is 10 percent. During the second interval, the increase is 11 million, but the starting population is now 110 million.

The second rate is \(11\div110\times100=10\) percent. Thus both equal intervals have the same percentage growth rate of 10 percent, even though the absolute increases differ: 10 million first and 11 million second. Option A is correct. Calling the second rate 11 percent incorrectly uses the original base of 100 million.

Correct answer: A. The second decade's growth applies to a larger population base

A percentage growth rate is applied to the population existing at the beginning of each period. After the first decade, the population is larger than it was initially. Therefore, the same 20 percent rate in the second decade is calculated on a larger base, producing a larger numerical addition even though the rate itself has not changed.

For example, if the initial population is 100, the first decade adds 20 and leaves 120. The second decade adds 20 percent of 120, which is 24. Thus 24 people are added in the second decade compared with 20 in the first. This is why option A is correct. The rate does not automatically rise; the base population rises.

Correct answer: A. Growth is mainly migration-driven

Population change can result from natural increase or migration. Natural increase is births minus deaths. If births and deaths are nearly balanced, natural increase contributes very little to the total change. A large positive immigration balance can still make the population grow.

Here, natural increase is nearly zero, yet heavy immigration is reported and the population is growing. Therefore the main source of growth is migration, specifically net immigration. Option A is correct. Growth is not zero because immigration adds people even when births and deaths nearly balance.

Correct answer: A. The difference between births and deaths

Natural increase is the difference between births and deaths. Total population change also includes net migration, but when net migration is nearly zero, migration adds almost nothing to the overall change. In that situation, the main source of growth is the balance between births and deaths within the country.

The relevant relation is total change = births − deaths + in-migration − out-migration. Since in-migration and out-migration are nearly equal, their difference is approximately zero. Therefore total growth is approximately births minus deaths, which is natural increase. Option A is correct. Area and density may describe population distribution, but neither determines the annual change as directly as the birth–death difference in this situation.

Correct answer: B. 2 percent

When natural increase and net migration are both given as numbers of people, add them to find the total population increase. Then compare that increase with the original population. The percentage rate is obtained by dividing the increase by the original population and multiplying by 100.

Total increase is \(600000+200000=800000\). The original population is 40,000,000, so the growth rate is \(800000\div40000000\times100=2\) percent. One percent would equal only 400,000 people in a population of 40 million. Therefore, the combined increase represents 2 percent, making option B correct.

Correct answer: A. Very large negative net migration

Natural increase is calculated as birth rate minus death rate. Since the birth rate is higher than the death rate, natural increase is positive. Total population growth also includes net migration. Therefore, for total growth to be negative despite positive natural increase, net migration must be sufficiently negative to outweigh that natural increase.

A large negative net migration means more people leave the country than enter it. This can make the total growth rate negative even while births exceed deaths. Hence option A is correct. Positive net migration would increase total growth, and a zero birth rate contradicts the information. Natural increase itself is not negative because the birth rate is higher than the death rate.

Correct answer: A. It is positive and larger than the natural decrease

Total growth equals natural increase plus net migration. If natural increase is negative, births are fewer than deaths and it reduces the population. If total growth is nevertheless positive, net migration must be positive enough to overcome that natural decrease. Therefore net migration is positive and larger in magnitude than the natural decrease, as stated in option A.

For example, if natural increase is −0.5 percent and net migration is +0.8 percent, total growth is +0.3 percent. The exact migration rate cannot be calculated without numerical rates, but its direction and minimum relative size are clear. A negative or zero migration rate would make total growth negative, not positive. Hence option A is the only valid conclusion.

Correct answer: A. A growing population base can offset the effect of a lower rate

Percentage growth and absolute growth are related but not identical. The percentage rate tells us what fraction of the existing population is added, while absolute growth tells us the actual number of people added. Absolute growth is found by multiplying the rate by the population base. As the base becomes larger, even a smaller percentage can represent a larger number of people.

For example, 2 percent of 10 million is 200000, but 0.9 percent of 30 million is 270000. Thus the rate can decline while the number added rises. Option A correctly identifies the growing population base as the explanation. Option B is false because the situation is mathematically possible; option C confuses rate with number, and option D is too restrictive because migration is not required for this result.

Correct answer: A. Because the same total rate can result from different combinations of births, deaths and migration

A total growth rate tells us the net result, but not the demographic processes that produced it. The total may reflect births, deaths, immigration, and emigration in different combinations. Two countries can therefore have the same rate while facing very different age structures, labour conditions, and future population trends.

For example, one country may grow because births greatly exceed deaths, while another may grow mainly because many migrants enter despite low natural increase. A third place could have high births and high deaths that nearly balance. Examining birth rate, death rate, natural increase, and net migration separately reveals these differences. Hence option A is correct. The other choices incorrectly deny the mathematical or demographic meaning of growth rate.

Correct answer: C. 21 percent

Percentage population growth is measured against the initial population, not the final population. The population increases from 50 million to 60.5 million, so the absolute increase is 10.5 million. Using the percentage-growth formula, \(\frac{\text{increase}}{\text{initial population}}\times100\), we get \(\frac{10.5}{50}\times100=21\) percent.

The same result can be seen by noting that 60.5 million is 1.21 times 50 million, which means the increase is 0.21 of the original amount. Therefore the correct choice is option C, 21 percent. Dividing by the final population would answer a different question and would incorrectly produce a smaller percentage, so the initial population must be used as the base.

Correct answer: A. Increase of 1200

Total population change combines natural change and migration. Natural change is births minus deaths: \(4800-3100=1700\). Migration change is in-migrants minus out-migrants: \(900-1400=-500\), meaning there is a net loss of 500 people through migration.

Adding both parts gives \(1700+(-500)=1200\). Thus the region’s population increases by 1,200 people, so option A is correct. Choosing 1,700 would count births and deaths but ignore the people who left. The negative migration balance reduces the natural increase; it does not reverse it completely in this case.

Correct answer: A. 18 per thousand

The natural growth rate is found by subtracting the death rate from the birth rate: \(31 - 9 = 22\) per thousand. Net migration is negative 4 per thousand, which means the country loses four people through migration for every thousand people. It must therefore be subtracted from natural growth: \(22 + (-4) = 18\) per thousand. The total growth rate is consequently 18 per thousand.

Option A is correct. Option B, 22 per thousand, is only the natural increase rate and ignores migration. Option C would result from treating the migration loss as a gain, while option D incorrectly adds all given figures. The negative sign is essential: it shows that out-migration exceeds in-migration. Thus the demographic and migration components together produce a positive but smaller total growth rate.

Correct answer: B. -0.5 percent

Total population growth combines two components: natural increase and net migration. Natural increase comes from births minus deaths, while net migration is the balance between people entering and leaving. Thus, if two of these quantities are known, the third can be found by subtraction.

Use \(\text{Total Growth}=\text{Natural Increase}+\text{Net Migration}\). Hence, \(\text{Net Migration}=1.8-2.3=-0.5\) percent. The negative sign means that out-migration is greater than in-migration by 0.5 percentage point. It does not mean that the total growth is negative; the country can still grow naturally. Therefore, option B is correct.

Correct answer: B. Decrease of 0.1 million

Total population change combines natural increase with migration. Natural increase is births minus deaths: \(1.2-0.8=0.4\) million, or 4 lakh. Net out-migration of 0.5 million means that 0.5 million people are lost from the country. Therefore, total change is \(0.4-0.5=-0.1\) million. A negative result means a decrease of 0.1 million, which is 1 lakh. Hence, option B is correct.

It is important not to stop after calculating births minus deaths, because migration also affects the total. The natural increase of 4 lakh is slightly smaller than the out-migration of 5 lakh, leaving a shortfall of 1 lakh. Option C gives only the natural increase and ignores migration, while option D ignores births and deaths. Thus, the complete balance supports option B.

Correct answer: B. 140000

The annual growth rate of 1.75 percent means that 1.75 out of every 100 people are added in one year, under the stated simple calculation. For a population of 8,000,000, calculate \(8000000\times\frac{1.75}{100}\). Since \(1.75\% = 0.0175\), the result is \(8000000\times0.0175=140000\).

Therefore, option B is correct: approximately 140,000 people are added in one year. This is a simple estimate and does not include complications such as changing rates, timing during the year, or compounding. The answer 175,000 would correspond to applying an incorrect percentage or arithmetic operation. The units are people, because the population number is multiplied by a dimensionless rate.

Correct answer: C. 50 percent

Total percentage growth compares the absolute increase with the initial population. The time period is useful for calculating an annual growth rate, but it is not needed when the question asks only for the total percentage increase over the whole period.

The absolute increase is \(30-20=10\) million. Divide this by the initial 20 million and multiply by 100: \((10\div20)\times100=50\%\). Therefore option C is correct. Dividing by 25 would answer a different question about an average annual measure, and using 30 million as the denominator would not give the standard percentage growth from the starting population.