Population Density

Correct answer: C. Number of people living per unit area

Explanation: Population density is a numerical measure of population concentration. It is commonly calculated as total population divided by the area occupied: Density = Population ÷ Area, usually expressed as persons per square kilometre. For example, if 20,000 people live in 100 square kilometres, the density is 200 persons per square kilometre. Thus, option C is correct. Density should not be confused with distribution: distribution describes the pattern of where people are located, whereas density measures how many occupy a unit of area. Rainfall, distance from the sea and elevation are physical characteristics, not the definition.

Correct answer: A. Hindrance to crop growth

Explanation: The governing concept is land degradation caused by the accumulation of soluble salts in soil. High salt concentration makes it harder for plant roots to absorb water because the soil solution has low water potential. Some salts can also produce toxic effects or disturb the availability and balance of essential nutrients. As a result, seeds may germinate poorly, plants may grow slowly, leaves may show injury, and crop yields can decline. Therefore, option A is correct because saline soil can hinder crop growth. It does not make all crops grow rapidly, increase rainfall, or automatically increase wildlife populations. Drainage improvement, careful irrigation, salt-tolerant crops, and appropriate soil-management practices may help reclaim or manage affected land.

Correct answer: A. Number of people living per unit area

Explanation: Population density means the number of people living in a given unit of area. It is generally expressed as the number of persons per square kilometre.

Correct answer: D. Water availability supports settlement and agriculture

Explanation: The correct answer is D: water availability supports settlement and agriculture. Every community needs water for drinking, cooking, sanitation, livestock, and other daily uses. Agriculture requires water from rainfall, rivers, lakes, canals, or groundwater, and many industries also use water. Consequently, regions with reliable water supplies are often more capable of supporting permanent settlements and larger populations. D is correct because it includes both human settlement and farming. A is wrong because water is a basic condition of life and strongly affects where people live. B is wrong because water is needed for households, farming, livestock, and services, not only industry. C is wrong because inland rivers, lakes, reservoirs, and groundwater can also support population. Water alone does not guarantee dense population, since relief, climate, jobs, and hazards also matter. Memory cue: water attracts people because it sustains life and livelihoods.

Correct answer: B. Number of people living per unit area

Explanation: Population density describes how many people live in a given unit of land area. It helps us understand whether people are spread thinly or concentrated closely together. Density is not the same as total population, because a large region may have many people but still be sparsely settled. It is also different from birth rate, which measures births, and from area, which measures the size of land.

To find density, divide the total population by the total area: \(D=\frac{P}{A}\). The result may be expressed as people per square kilometre or another unit of area. Therefore, the correct answer is option B, the number of people living per unit area. Option A gives only the numerator, not the relationship between population and land.

Correct answer: A. \(Population\ Density=\frac{Total\ Population}{Total\ Area}\)

Explanation: Population density tells us how many people live, on average, in one unit of land area. It is a measure of population concentration, not the total number of people alone. The usual unit is persons per square kilometre, although another area unit may be used if stated.

To calculate it, divide the total population by the total area: \(\text{Population Density}=\frac{\text{Total Population}}{\text{Total Area}}\). Multiplication would give an unrelated quantity, while area divided by population gives area per person. Birth rate and death rate are used for population change, not density. Therefore, option A is correct.

Correct answer: B. Persons per square kilometre

Explanation: Population density tells us how many people live in a fixed unit of land area. It is a measure of concentration, not a measure of population growth, travel distance, or family size. The usual geographical unit is persons per square kilometre, because this allows populations of different regions to be compared fairly. A higher value means more people live, on average, in each square kilometre.

Therefore, option B is correct: persons per square kilometre. The expression has people as the numerator and area as the denominator. “Kilometres per person” reverses the relationship, while “percent per year” describes a rate of change and not density. The unit “metres per family” is unrelated to this geographical measure.

Correct answer: C. 100 persons per square kilometre

Explanation: Population density is found by dividing the number of people by the land area they occupy. The answer must therefore be expressed as persons per square kilometre. This calculation compares the population with the size of the region, so a larger population does not automatically mean a larger density unless the area is also considered.

Use \(\text{Density}=\frac{\text{Population}}{\text{Area}}\). Substituting the given values gives \(\frac{100000}{1000}=100\) persons per square kilometre. Thus every square kilometre contains 100 people on average. Option A would result from an incorrect division, while option D reverses the scale. Therefore, option C is correct.

Correct answer: C. 100 persons per square kilometre

Explanation: Population density tells us how many people live, on average, in one unit of area. It is calculated by dividing the total population by the total land area, and the unit here is persons per square kilometre. This measure allows regions of different sizes to be compared fairly. A larger population does not automatically mean greater density if the area is also much larger.

Using the given figures, the calculation is \(\text{Density}=\frac{50000}{500}=100\) persons per square kilometre. Therefore, option C is correct. Option B would result from dividing by 1,000, while option D incorrectly treats the area as if it were the divisor in the wrong direction. The answer must include the unit as well as the number.

Correct answer: B. It will be higher

Explanation: Population density tells us how many people live in a unit of area. It is calculated as population divided by area, often expressed as persons per square kilometre. When two regions have exactly the same area, the denominator in the calculation is the same for both regions. The region with more people must therefore have more people per unit area.

For example, if one region has 20,000 people and another has 10,000 people over the same area, the first region will have twice the density. Equal area does not mean equal density when population totals differ. Thus the larger population produces the higher density, making option B correct. The other choices reverse or deny this relationship.

Correct answer: A. It will be higher

Explanation: Population density measures how many people occupy one unit of area. It is calculated as population divided by area, written as (Population/Area). When two regions have exactly the same population, the region with less land has to accommodate the same number of people in a smaller space. Consequently, there are more people per square kilometre there, so its density is higher.

For example, if each region has 100,000 people, an area of 1,000 square kilometres gives a density of 100 people per square kilometre. An area of 500 square kilometres gives 200 people per square kilometre. Thus the smaller region has the greater density, making option A correct. Option B reverses the relationship, while option C would be true only if the areas were also equal. The comparison is certain because the populations are stated to be equal.

Correct answer: A. Fertile river plain

Explanation: Population density is generally high where people can obtain water, food, shelter, transport, and livelihoods relatively easily. Fertile river plains usually offer dependable water, productive soils, level land, farming possibilities, and routes for movement and trade. These advantages can support villages, towns, and cities over long periods.

Permanent ice regions, uninhabited deserts, and very high mountain peaks usually create severe limits through cold, lack of water, poor soils, steep terrain, or difficult transport. Some people may live in such places, but they generally do not support large concentrations. Thus option A is the best general answer because fertile river plains provide several conditions favorable to dense settlement.

Correct answer: C. Hot arid desert

Explanation: Population density means the average number of people living in a unit of land area. Regions with dependable water, moderate conditions, fertile land, transport, employment, and services usually attract more permanent residents. Hot arid deserts generally have very little water and may also experience extreme heat, poor soils, and difficult travel. These conditions restrict agriculture, settlement, and the ability of large communities to remain there.

Option C is correct because hot arid deserts normally support fewer people per square kilometre than productive and urban regions. An irrigated plain can support intensive farming, while a metropolitan area and an industrial city offer jobs, housing, transport, and services. These alternatives may have high density, although individual examples can vary. The word “generally” is important: small settlements or resource projects may exist in deserts, but the overall density is usually low.

Correct answer: A. To compare population concentration among regions

Explanation: Population density is a measure of how many people occupy a unit of area. It is commonly calculated as population divided by land area, such as persons per square kilometre. Because the same unit is used for different places, density helps us compare how strongly people are concentrated in regions, states, or countries.

Therefore option A is correct: density is mainly used to compare population concentration among regions. It does not directly give the birth rate or death rate, because those are demographic rates based on births or deaths over time. It also does not mean only the total area. A large region can have a low density, while a smaller region can have a high density if many people live in it. Density is an average, so local crowding may vary within the region.

Correct answer: A. Density will increase

Explanation: Population density tells us how many people live, on average, in one unit of area. It is found by dividing total population by total area. Therefore, density depends on both the number of people and the space available for them. If the space does not change but the number of people rises, more people are present in each square kilometre on average. The correct choice is A, density will increase.

For example, if 1,000 people live in 10 square kilometres, density is 100 people per square kilometre. If the population becomes 1,200 while the area remains 10 square kilometres, density becomes 120 people per square kilometre. Thus the ratio increases. Density does not become zero or remain unchanged, because the numerator has increased while the denominator is constant.

Correct answer: B. It will decrease

Explanation: Population density means the average number of people living in one unit of area, usually one square kilometre. It is found by dividing population by area. If the area does not change but the number of people becomes smaller, fewer people are spread across exactly the same land. Therefore the density must decrease. The correct choice is B, “It will decrease.”

For example, suppose 10,000 people live in 100 square kilometres. The density is 100 people per square kilometre. If the population falls to 8,000 and the area remains 100 square kilometres, the density becomes 80 people per square kilometre. The land has not changed, so no other factor can make the density rise or stay equal. A decrease in population with a fixed area directly lowers density.

Correct answer: B. 100 persons per square kilometre

Explanation: Population density tells us how many people live, on average, in one square kilometre. It is found by dividing the total population by the total land area. The unit must be written as persons per square kilometre because population is being related to area. A higher quotient means more people are concentrated in each unit of land, while a lower quotient means fewer people are present on average.

Here, the calculation is \(200000 \div 2000 = 100\). Thus, the region has an average density of 100 persons per square kilometre, so option B follows. Option A would result from an incorrect division, while options C and D are too large. This is an average figure; it does not mean that every square kilometre necessarily contains exactly 100 people.

Correct answer: C. 200 persons per square kilometre

Explanation: Answer: C, 200 persons per square kilometre. Population density tells us the average number of people living in one unit of area. The formula is density = total population ÷ total area. Here, population = 60,000 and area = 300 square kilometres. Therefore, density = 60,000 ÷ 300 = 200 persons per square kilometre. This means that if the whole region were considered on average, each square kilometre would contain 200 people; it does not mean that people are distributed perfectly evenly. A is incorrect because 60,000 has not been divided correctly by 300. B is also too low, and D incorrectly treats the area value as the answer. Always write the unit because density is not simply a number. Memory cue: population goes on top, area goes below—people per square kilometre.

Correct answer: B. 100 persons per square kilometre

Explanation: Answer: B, 100 persons per square kilometre. Density is calculated by dividing the number of people by the area occupied: density = population ÷ area. Substituting the values gives 90,000 ÷ 900. Cancel two zeros from both numbers or divide directly: 90,000/900 = 100. Thus the average density is 100 persons per square kilometre. A and C are incorrect because they do not give the correct quotient. D is the area number copied as the answer; it confuses square kilometres with people per square kilometre. The unit is important: the numerator is people and the denominator is square kilometres. Memory cue: never divide area by population for density; use people divided by land area.

Correct answer: A. On average 250 people live in each square kilometre

Explanation: A density of 250 persons per square kilometre describes an average relationship between population and area. It means that if the whole region were divided conceptually into one-square-kilometre units, the population would average 250 persons in each unit. Some units may have more people and others fewer; the statement does not require an exactly equal distribution.

Thus option A is correct. The figure does not say that the entire region contains only 250 people, because the total population depends on the region’s total area. It also does not mean the area is 250 square kilometres, nor that each person has 250 square kilometres of land. If area and density are known, total population can be found by multiplying them, but the density alone gives only the average per unit area.

Correct answer: A. Relatively many people in a small area

Explanation: High population density describes how many people live within a given unit of land. When a relatively large number of people live in a small area, the area is called densely populated. Density is not simply the total number of people, and it is not the same as birth rate or the size of the territory. It usually expresses average people per square kilometre.

Therefore, option A is correct because it directly states that many people live in a small area. Option B describes low density, while option C concerns births and option D concerns area size alone. A large population can still have low density if it is spread across a very large area, so both population and area must be considered together.

Correct answer: A. Region A

Explanation: Population density measures the number of people living in each unit of area. A larger numerical value means that more people occupy each square kilometre, so the population is more concentrated there. Region A has a density of 300 persons per square kilometre, whereas region B has only 100 persons per square kilometre.

Comparing the two values gives 300 > 100. Thus every square kilometre of A contains, on average, three times as many people as every square kilometre of B, assuming the figures use the same units and method. No additional information about total area is needed because the densities are already provided. Therefore option A is correct.

Correct answer: A. A level plain with jobs and transport

Explanation: High population density is more likely where physical conditions and human opportunities support settlement. A level plain is easier to build on, cultivate, and connect with roads and railways. If it also has employment, reliable water, schools, health services, markets, and transport, it can attract many residents and sustain a large population. The same land area can therefore contain many more people than a remote or physically harsh region.

Option A is correct because it combines a favourable landform with jobs and transport. The other choices describe places that usually discourage dense settlement: an ice-covered plateau has severe climate, a waterless desert lacks a basic resource, and an inaccessible mountain peak has difficult slopes and limited infrastructure. Density is not determined by landform alone, but the combination in option A creates several strong attractions for population concentration.

Correct answer: A. Population increasing while area remains the same

Explanation: Density is a ratio between population and area: \(\text{density}=\frac{\text{population}}{\text{area}}\). If the area does not change and more people live there, the same amount of land must accommodate more people. Consequently, the average number of people per square kilometre increases. This is a direct effect and does not require any assumption about the kind of settlement.

Option A states exactly this situation, so it is correct. If population continuously decreases, density generally falls when area is unchanged. If area increases while population stays constant, people are spread over more land and density falls. Complete out-migration would also reduce the population rather than increase its density. Thus the other choices do not describe an increase.

Correct answer: A. Population decreasing while area remains the same

Explanation: Population density means the average number of people living in a unit of area, usually one square kilometre. It depends on two things: population and area. When the area stays unchanged but the number of people falls, fewer people are present in each square kilometre. Therefore, density decreases. This is the situation described by option A.

Option B would increase density because more people occupy the same area. Option D would also usually increase density because incoming migrants add people. Option C could increase density because the same population would be concentrated in a smaller area. Thus, a fall in population with unchanged area is a clear cause of decreasing density.