Population Density

Correct answer: C. Favorable conditions for agriculture and settlement support population

Explanation: Fertile plains often have deep, productive soils, relatively level land, and conditions suitable for cultivation. They can provide reliable food supplies and support villages, towns, and employment connected with farming and trade. Their flat surface also generally makes construction, roads, railways, and movement easier than in steep or rugged areas. These combined advantages encourage people to settle in them over long periods.

Option C is correct because favorable agricultural and settlement conditions can support a large population. Permanent ice would prevent ordinary settlement, and a plain is not necessarily small. The absence of transport would usually discourage concentration rather than cause it. Thus the important explanation is not one single feature but the combined effect of fertile land, food production, settlement space, and accessibility. Therefore C follows.

Correct answer: D. Yes because a regional average can hide local differences

Explanation: A regional density is an average for the whole region. It does not mean that every part of the region has exactly the same number of people per square kilometre. A large region may include a crowded city, villages, farmland, mountains, forests, or nearly empty land. Thus, a city can have high density even when the average density of the entire region is low. The correct choice is D.

Imagine a region containing one compact city and a very large sparsely settled area around it. The city may have many people in a small space, while the surrounding land has very few people. When population and area are combined for the regional calculation, the empty or lightly settled land lowers the average. Options A and B wrongly treat an average as an identical value everywhere; option C is unrelated to the definition.

Correct answer: A. The country with half the area will have higher density

Explanation: Population density is calculated as \(\text{Population density}=\frac{\text{Population}}{\text{Area}}\). When two countries have the same population, the country occupying less land has more people per unit of area. Therefore, if one country has half the area of the other, the same number of people is concentrated into half as much space. Its density will be twice as high. The correct choice is A.

For example, suppose both countries have 1,000,000 people. If the larger country covers 20,000 square kilometres, its density is 50 people per square kilometre. A country with the same population but 10,000 square kilometres has density 100 people per square kilometre. Thus, reducing area while keeping population constant increases density. Birth rate is not needed for this comparison, so option D is unsuitable.

Correct answer: B. Population must be understood in relation to area

Explanation: The correct answer is B. Population density means the number of people living in relation to a given area of land. A common expression is \(\text{density}=\frac{\text{population}}{\text{area}}\), often measured in persons per square kilometre. Therefore, knowing only the total population is not enough. A large region may contain many people but still have low density, while a small region may have fewer people but a much higher density.

Density is useful for comparing how concentrated or dispersed populations are, and it helps explain population distribution. It applies to rural areas, cities, states, and countries, not only to cities. Option A ignores area, C wrongly limits the concept to urban places, and D incorrectly separates density from distribution. The essential idea is always population considered together with land area.

Correct answer: A. Concentration of people per unit area

Explanation: Population density measures the spatial concentration of people. It tells us the average number of people living in one unit of land area, such as one square kilometre. The basic relationship is density equals population divided by area. This allows a meaningful comparison between places of different sizes, because total population alone can be misleading.

Option A is therefore correct. A region with many people in a small area has a high density, while a region with few people across a large area has a low density. Density does not measure only births, total births, deaths, or total area. Birth and death rates describe demographic events over time, whereas density describes where people are located in relation to land. It is an average and may hide differences between crowded cities and sparsely settled rural or remote parts.

Correct answer: B. Total area

Explanation: Population density measures how many people occupy an average unit of land. The standard relationship is \(Population\ Density=\frac{Total\ Population}{Total\ Area}\). Thus, the numerator is the complete number of people and the denominator is the complete area of the region, normally in square kilometres or another stated unit. The result tells us the average number of persons per unit area.

Therefore option B, total area, is correct. Total births and total deaths are demographic flow measures used to study natural change, not the space available to people. Total migrants may describe part of population movement, but it is not the denominator in the density formula. The units also confirm the answer: persons divided by square kilometres produces persons per square kilometre.

Correct answer: B. On average 80 people live in each square kilometre

Explanation: A density of 80 persons per square kilometre is an average measure. It means that if the region were represented as equal one-square-kilometre units, the total population would correspond to about 80 people for each such unit. It does not say that the whole region contains only 80 people, because the region may cover many square kilometres. Nor does it describe family size or directly state the region’s area.

Option B is correct because it expresses the meaning and unit of the density value accurately. For example, if the area were 10 square kilometres and the density were uniform, the population would be about 800 people; in a real region, people may be clustered unevenly, but the average would still be 80 per square kilometre. Options A, C, and D confuse density with total population, area, or household size.

Correct answer: C. 200 persons per square kilometre

Explanation: Population density tells us how many people live in each square kilometre. The basic formula is \(\text{density}=\text{total population}/\text{total area}\). The units matter: when population is counted in people and area in square kilometres, the answer is expressed as persons per square kilometre.

Here, divide 30,000 by 150. Since \(150\times200=30,000\), the quotient is 200. Thus the density is 200 persons per square kilometre, so option C is correct. The other numbers result from using an incorrect division or from confusing the given area with the answer. No conversion is needed because the area is already given in square kilometres.

Correct answer: C. 200 persons per square kilometre

Explanation: Population density is calculated by dividing the total population by the total land area. It gives the average number of people living in one square kilometre. The area must be kept in square kilometres because the answer choices use that unit. This calculation assumes that the population is spread unevenly in reality but reports one average value for the whole region.

Use the formula \(\text{Density}=\frac{\text{Population}}{\text{Area}}\). Substituting the given values gives \(\frac{84000}{420}=200\) persons per square kilometre. Thus option C is correct. The other numbers do not result from the required division; in particular, 420 is the area, not the density. The answer means an average of 200 people in each square kilometre.

Correct answer: B. Dense metropolitan region

Explanation: Population density is generally high where many people live within a limited area. Metropolitan regions usually concentrate homes, workplaces, schools, hospitals, markets, transport systems, and other services. These opportunities attract residents and support compact settlement. Density can vary within a city, but a large metropolitan region is normally denser than a sparse rural settlement or an almost uninhabited physical environment.

Option B is therefore correct. A sparse rural area has people spread over a wider area, while deserts and high ice-covered regions usually have strong environmental limits on permanent settlement. The question asks about the general pattern, not every exceptional location, so the dense metropolitan region is the best choice.

Correct answer: B. 150000 people

Explanation: Total population can be found by multiplying population density by total area. The relationship is \(\text{Population}=\text{Density}\times\text{Area}\). Here, the density is 150 persons per square kilometre and the area is 1,000 square kilometres. Multiplying these values gives the number of people represented by all the square kilometres together. Therefore, the correct choice is B, 150,000 people.

The calculation is \(150\times1000=150000\). The units also confirm the result: persons per square kilometre multiplied by square kilometres leaves persons. Option A, 15,000, would result from using only 100 square kilometres or from an incorrect place-value calculation. The other choices do not follow from the stated density and area. No rounding is needed because both given values are exact for this exercise.

Correct answer: C. 2000 people

Explanation: When population density remains constant, the population in a region depends directly on its area. To find the number of people, multiply the density per square kilometre by the number of square kilometres. This works because every one of the five square kilometres is assumed to contain the same average number of people, namely 400.

The required calculation is population = density × area. Therefore, population = 400 × 5 = 2000 people. Hence, option C is correct. The number 400 is only the population in one square kilometre, not in all five square kilometres. Multiplying by five is necessary to include the whole area. The answer assumes the stated density is uniform throughout the region.

Correct answer: A. Fewer people live per unit area

Explanation: Population density is a measure of how many people occupy a given amount of land. It is usually expressed as people per square kilometre or another unit of area. The word “low” means that the average number of people within each unit of land is small compared with a more densely populated place.

Therefore, option A gives the direct meaning: fewer people live per unit area. Low density by itself does not tell us why the figure is low. It does not prove that births are few, deaths are high, or the total area is small. Those conditions may influence population patterns, but they are separate facts. The definition of density is a population-to-area relationship, so A is the only suitable choice.

Correct answer: A. More people live per square kilometre

Explanation: High population density is a measure of concentration, not simply of the total number of people or the physical size of a region. It means that many people live within each unit of area, such as each square kilometre. A small city can therefore have a high density even if its total population is not the largest.

Option A states exactly this meaning: more people live per square kilometre. Option B is the opposite of high density. Option C is not always true because a dense region may also have a large total population. Option D is also not necessary, since density can be high in a small area. Therefore, option A is the only generally correct statement.

Correct answer: C. 300 persons per square kilometre

Explanation: Population density is calculated by dividing the number of people by the land area they occupy. Here the population is 96,000 and the area is 320 square kilometres. The calculation is \(\mathrm{Density}=\frac{96{,}000}{320}=300\) persons per square kilometre. This means that the area has an average of 300 people living in each square kilometre.

Therefore, option C is correct. The unit is important: people divided by square kilometres gives persons per square kilometre. Option A and option B result from using an incorrect division, while option D simply repeats the area value and does not calculate density. The answer does not mean that every square kilometre has exactly 300 residents; it is an average for the whole region. The supplied answer and calculation are correct.

Correct answer: C. 200 persons per square kilometre

Explanation: Population density is found by dividing population by area. Here the population is 50,000 and the area is 250 square kilometres, so \(\text{density}=\frac{50000}{250}=200\) persons per square kilometre. The unit is important: the result tells us how many people correspond, on average, to each square kilometre. It is not a total population count and should not be reported without the area unit.

Option C is correct. A useful check is that \(250\times200=50,000\), which returns the given population. Option A would imply only 25,000 people in the stated area, option B would imply 37,500 people, and option D would imply 62,500 people. These checks show why the division must use population as the numerator and area as the denominator.

Correct answer: B. Density will double

Explanation: Answer: B, density will double. Use the formula density = population ÷ area. The population is fixed, while the area changes from A to A/2. Thus the new density is P ÷ (A/2), which equals 2P/A, or twice the original density. A numerical example makes this clear: 1,000 people in 10 square kilometres give 100 people per square kilometre. If the measured area becomes 5 square kilometres while the population remains 1,000, the density becomes 200 people per square kilometre. A reverses the relationship. C ignores that the denominator changed. D is impossible because the population has not become zero. This is an inverse relationship: when fixed population is divided by a smaller area, density increases.

Correct answer: B. Density becomes three times

Explanation: Population density tells us how many people occupy each unit of area. It is calculated as
\(\text{Density}=\frac{\text{Population}}{\text{Area}}\)\u0001. When the area does not change, multiplying the population by three multiplies the number of people per square kilometre by three as well.

Thus option B is correct. For example, if an area had 100 people per square kilometre, it would have 300 people per square kilometre after the population tripled, provided its area stayed fixed. Options A and D describe decreases, while C would be true only if population also stayed unchanged or if some other condition offset the increase.

Correct answer: C. Extremely cold polar region

Explanation: Very low population density is usually found where physical conditions make permanent settlement, farming, transport, or employment difficult. Extremely cold polar regions have severe temperatures, extensive ice or frozen ground, long difficult winters, and very limited opportunities for agriculture. These conditions generally restrict both settlement and population concentration.

Therefore, option C is correct. Fertile river valleys and irrigated plains can support crops, water supply, and settlements, while industrial metropolises offer many jobs and services and are usually densely populated. The word “generally” matters because a few research stations or small settlements may exist in polar regions, but the overall density remains very low.

Correct answer: A. Reliable water and fertile land

Explanation: Answer: A, reliable water and fertile land. Water is needed for drinking, household use, farming and many economic activities. Fertile land can support productive agriculture and food supply, making regular settlement easier. Therefore these conditions can help an area support a larger population and a higher density, although they do not guarantee it by themselves. B generally makes living and farming difficult because permanent ice and extreme cold restrict access and cultivation. C prevents normal life and agriculture. D describes terrain that is difficult to build on, travel across and cultivate. Rainfall, soil, relief and water are natural factors, but this question asks for the condition most clearly favourable to dense settlement. Memory cue: dependable water plus usable fertile land generally encourages settlement.

Correct answer: A. Increase in employment opportunities

Explanation: Employment opportunities are an important human factor affecting where people live. When a region offers jobs, workers and their families may move there to earn income. If the region’s area does not expand as quickly as its population, the number of people per unit of area increases. This raises population density.

The other choices describe conditions that usually discourage settlement or cause people to leave: closing industries removes jobs, insecurity creates risk, and loss of transport reduces access. Employment growth can also support markets and services, making the region more attractive. It does not guarantee that density will rise in every case, but it can clearly increase it through in-migration. Therefore option A is correct.

Correct answer: C. 300 persons per square kilometre

Explanation: Population density is calculated by dividing the total population by the total area. The required unit is persons per square kilometre because the population is given in people and the area in square kilometres. Here the calculation is \(72000\div240\). Both numbers can be divided by 24, giving \(7200\div24=300\). Therefore, the region has 300 persons per square kilometre, so option C is correct.

A useful check is to multiply the proposed density by the area: \(300\times240=72000\), which returns the given population. The other choices would produce different totals for the same area. For example, 250 people per square kilometre would give only 60000 people. Thus, the correct operation is population divided by area, not area divided by population, and the answer is option C.

Correct answer: C. 150,000 people

Explanation: Answer: C, 150,000 people. Density means population per unit area, so the relationship is density = population ÷ area. Rearranging it gives population = density × area. Substitute the values: 250 persons per square kilometre × 600 square kilometres = 150,000 persons. The square-kilometre units cancel, leaving people, which confirms that the operation is correct. A is too small and does not result from 250 × 600. B is also not the product of the given values. D incorrectly uses the density number without multiplying it by the full area. The key distinction is that density is a rate, not the total population. Memory cue: to find population, multiply density by area; to find density, divide population by area.

Correct answer: B. 10000 people

Explanation: Population density is the average number of people living in one unit of area. If density is 50 persons per square kilometre and the area is 200 square kilometres, the total population is found by multiplying these two quantities. The square-kilometre units cancel appropriately, leaving the number of persons. This is the reverse of finding density from population and area.

Use the relation \(\text{Population}=\text{Density}\times\text{Area}\). Therefore, \(50\times200=10,000\) people. The answer 5,000 would result from an incorrect multiplication or using only part of the data, while 20,000 and 25,000 are too large. Hence, option B is correct.

Correct answer: C. 500 square kilometres

Explanation: The density formula connects population, area, and density: \(\text{Density}=\frac{\text{Population}}{\text{Area}}\). When population and density are known, the area can be found by rearranging the relationship. This is useful because density states how many people are present in each square kilometre.

Multiply both sides by area and divide by density to obtain \(\text{Area}=\frac{\text{Population}}{\text{Density}}\). In this case, \(\frac{150000}{300}=500\) square kilometres. Checking the result, \(500\times300=150000\), so it agrees with the given population. Therefore, option C is correct; the other choices do not satisfy the formula.