NCERT Solutions for Class 12 Geography Practical Work in Geography II Chapter 3: Graphical Representation of Data

Chapter at a glance

Exercise Questions

Question 1 (i)

Which one of the following map shows the population distribution:
(a) Choropleth maps (b) Isopleth maps (c) Dot maps (d) Square root maps

Answer

Dot maps show the distribution of phenomena such as population — each dot represents a fixed number of people, placed where they actually live.

3. Dot maps

Question 1 (ii)

Which one of the following is best suited to represent the decadal growth of population?
(a) Line graph (b) Bar diagram (c) Circle diagram (d) Flow diagram

Answer

A line graph is best suited to show time-series data such as the decadal growth of population.

1. Line graph

Question 1 (iii)

Polygraph is constructed to represent:
(a) Only one variable (b) Two variables only (c) More than two variables (d) None of the above

Answer

A polygraph is a line graph in which two or more variables (more than two, e.g. growth rates of several states) are shown by separate lines for comparison.

3. More than two variables

Question 1 (iv)

Which one of the following maps is known as “Dynamic Map”?
(a) Dot map (b) Choropleth (c) Isopleth (d) Flow map

Answer

Flow maps show the movement of goods, people or vehicles along routes and are therefore called dynamic maps.

4. Flow map

Question 2 (i)

What is a thematic map?

Answer

A thematic map shows the spatial distribution of a particular theme or phenomenon (e.g. population density, rainfall, crop production, literacy) rather than general features. Data are represented by symbols, dots, shades, lines or flows. Types include dot maps, choropleth maps, isopleth maps and flow maps.

A thematic map shows the spatial distribution of a particular theme (population, rainfall, crops, literacy) using dots, shades, isolines or flow lines — e.g. dot, choropleth, isopleth and flow maps.

Question 2 (ii)

Differentiate between multiple bar diagram and compound bar diagram.

Answer

A multiple bar diagram shows two or more variables as separate bars side by side for comparison; a compound bar diagram shows the components of a total stacked within a single bar.

Question 2 (iii)

What are the requirements to construct a dot map?

Answer

1. An administrative/outline map of the area showing the boundaries of units (states, districts).
2. Data of the phenomenon for each unit (e.g. population of each district).
3. Decision on the value of each dot (e.g. 1 dot = 10,000 persons) and the size of the dot.
4. Knowledge of the physical features (relief, drainage, forests, deserts) of the area so that dots are placed where the phenomenon actually occurs and not in uninhabited areas.

A dot map needs an outline map with administrative boundaries, data for each unit, a chosen dot value and dot size, and knowledge of the area’s physical features so dots are placed realistically.

Question 2 (iv)

Describe the method of constructing a traffic flow map.

Answer

1. Take a route map showing the desired transport routes (roads/railways) connecting the places.
2. Collect data on the volume of traffic (number of vehicles, goods, passengers) along each route.
3. Select a suitable scale to represent the volume of traffic — the width (thickness) of the flow line is proportional to the volume (e.g. 1 mm = 50 vehicles).
4. Draw lines/bands of proportional thickness along each route; arrows may show direction.
5. Give a title, key/legend showing the scale, and source.

Take a route map and traffic data, choose a scale relating line thickness to traffic volume, draw bands of proportional width along each route (with arrows for direction), and add a title, legend and source.

Question 2 (v)

What is an Isopleth map? How an interpolation is carried out?

Answer

An isopleth map shows the distribution of a phenomenon that changes gradually and continuously over space (temperature, pressure, rainfall, relief) using isolines — lines joining places of equal value (isotherms, isobars, isohyets, contours).

Interpolation is the method of estimating intermediate values between two known values at points, to locate where an isoline passes: 1. Decide the interval for isolines (e.g. every 10 cm of rainfall). 2. Between two stations with known values, find the position of the required value by proportional distance: distance from the lower point = (required value − lower value) ÷ (higher value − lower value) × distance between points. 3. Mark these points and join points of equal value with smooth lines.

E.g. if station A has 20 cm and B has 40 cm, the 30 cm isohyet passes midway between them.

An isopleth map uses isolines joining places of equal value (isotherms, isobars, isohyets) to show continuously varying phenomena. Interpolation estimates intermediate values between known points by proportional distance (e.g. the 30 cm isohyet lies midway between stations with 20 and 40 cm); points of equal value are then joined by smooth lines.

Question 2 (vi)

Describe and illustrate important steps to be followed in preparing a choropleth map.

Answer

Choropleth maps show data as average values per unit area of administrative units (e.g. population density, % literacy) using different shades or colours.

Steps: 1. Collect data for each administrative unit (e.g. percentage of rice production by state). 2. Arrange the data in ascending or descending order and find the range. 3. Group the data into 3–5 classes (e.g. low, medium, high) with suitable class intervals. 4. Decide a shading/colour scheme — darker shades for higher values and lighter for lower values (of the same colour, or patterns). 5. Shade each unit on the outline map according to its class. 6. Add a title, legend (key), scale and source.

Illustration (Activity 4(d) data — % of rice production): low 6.4–8.5 (Tamil Nadu, Bihar — light shade); medium 8.6–12.5 (Punjab — medium shade); high 12.6–14.6 (West Bengal, Uttar Pradesh, Andhra Pradesh — dark shade).

Collect data per administrative unit, arrange it and find the range, group into 3–5 classes, choose shades (darker for higher values), shade each unit by class on an outline map, and add a title, legend, scale and source — e.g. rice production classes: low (Tamil Nadu, Bihar), medium (Punjab), high (West Bengal, UP, Andhra Pradesh).

Question 2 (vii)

Discuss important steps to represent data with help of a pie-diagram.

Answer

1. Calculate the share of each component in the total (percentages or values).
2. Convert into degrees: angle = (component value ÷ total) × 360°, or percentage × 3.6.
3. Arrange the components in descending order (optional) and check that the angles add up to 360°.
4. Draw a circle of suitable radius (radius may be proportional to the total if comparing two totals — proportional circles).
5. Draw a vertical line from the centre to the top (12 o’clock) and mark the angles clockwise with a protractor, starting with the largest component.
6. Shade/colour each sector differently; add labels, a legend, title and source.

Calculate each component’s share, convert it to degrees (value ÷ total × 360°), check the total is 360°, draw a circle, mark the sectors clockwise from the vertical radius with a protractor (largest first), shade them differently and add labels, legend, title and source.

Question Activity – 1

Represent the following data with the help of suitable diagram. (Decennial growth %: 1911 – 0.35, 1921 – 8.27, 1931 – 19.12, 1941 – 31.97, 1951 – 41.42, 1961 – 26.41, 1971 – 38.23, 1981 – 46.14, 1991 – 36.47, 2001 – 31.13.)

Answer

Time-series data are best shown by a line graph (census years on the X-axis, growth % on the Y-axis, scale 1 cm = 10%).

(Note: the values given in the textbook table do not match India’s published decadal growth rates, e.g. 1911 = 5.75%, 1951 = 13.31%; the graph plots the data as given.)

A line graph is drawn with census years on the X-axis and growth (%) on the Y-axis; the given values rise from 0.35 (1911) to a peak of 46.14 (1981), with a dip in 1961, and fall to 31.13 (2001).

Question Activity – 2

Represent the following data with the help of suitable diagram. (India: literacy ratio — person, male, female — and enrolment ratio — primary and upper primary, boys, girls, total — for 1950-51 and 1999-2000.)

Answer

To compare the two years for several categories, a multiple bar diagram is suitable.

Interpretation: literacy and enrolment rose sharply; the gender gap narrowed but remained (female literacy 54.2% vs male 75.8%).

A multiple bar diagram compares 1950-51 and 1999-2000 for each category: literacy rose from 18.3% to 65.4% (female 8.86% to 54.2%) and enrolment rose sharply at both primary and upper primary levels, with a narrowing but continuing gender gap.

Question Activity – 3

Represent the following data with help of pie-diagram. (India: land use — Net sown area 42, 46; Forest 14, 22; Not available for cultivation 17, 14; Fallow land 10, 8; Pasture and tree 9, 5; Culturable waste land 8, 5 — for 1950-51 and 1998-2001, in per cent.)

Answer

Angles (per cent × 3.6)

Interpretation: net sown area and forest (notified) increased; fallow, pasture and culturable waste declined.

Two pie diagrams are drawn with angles = % × 3.6 (1950-51: 151.2°, 50.4°, 61.2°, 36°, 32.4°, 28.8°; 1998-2001: 165.6°, 79.2°, 50.4°, 28.8°, 18°, 18°), showing an increase in net sown area and forest and a decline in fallow, pasture and culturable waste land.

Question Activity – 4

Study the table (Area and production of rice in major States — West Bengal 5,435 thousand ha (12.3%), 12,428 thousand tonnes (14.6%); Uttar Pradesh 5,839 (13.2%), 11,540 (13.6%); Andhra Pradesh 4,028 (9.1%), 12,428 (13.5%); Punjab 2,611 (5.9%), 9,154 (10.8%); Tamil Nadu 2,113 (4.8%), 7,218 (8.5%); Bihar 3,671 (8.3%), 5,417 (6.4%)) and draw: (a) a multiple bar diagram to show area under rice in each State; (b) a pie-diagram to show the percentage of area under rice in each State; (c) a dot map to show the production of rice in each State; (d) a choropleth map to show the percentage of production of rice in States.

Answer

(a) Bar diagram of area under rice: (only one variable — area — is given per state, so a simple bar for each state is drawn; area and production could be shown side by side as a multiple bar.)

(b) Pie diagram of percentage of area (the six states together have 53.6% of India’s rice area; the rest is “other states”):

(c) Dot map of production – take an outline map of India with state boundaries; choose 1 dot = 5 lakh tonnes (500 thousand tonnes):

Place the dots evenly over the rice-growing (plain, irrigated) parts of each state — e.g. the Ganga delta in West Bengal, the coastal deltas of Andhra Pradesh, the Kaveri delta in Tamil Nadu — and give a key.

(d) Choropleth map of % production – classes and shades:

Shade the states on an outline map accordingly, with a legend. (Note: the table gives the same production figure — 12,428 — for West Bengal and Andhra Pradesh but different percentages, which appears to be a misprint; the given figures are used.)

1. Draw bars of area for each state (UP 5,839 highest, Tamil Nadu 2,113 lowest). (b) Pie angles: UP 47.5°, West Bengal 44.3°, Andhra Pradesh 32.8°, Bihar 29.9°, Punjab 21.2°, Tamil Nadu 17.3°, other states 167°. (c) Dot map with 1 dot = 5 lakh tonnes: West Bengal 25, Andhra Pradesh 25, UP 23, Punjab 18, Tamil Nadu 14, Bihar 11 dots. (d) Choropleth: low (6.4–8.5%) Bihar, Tamil Nadu; medium (8.6–12.5%) Punjab; high (12.6–14.6%) West Bengal, UP, Andhra Pradesh.

Question Activity – 5

Show the following data of temperature and rainfall of Kolkata with a suitable diagram. (Temperature °C / rainfall cm: Jan 19.6/1.2, Feb 22.0/2.8, Mar 27.1/3.4, Apr 30.1/5.1, May 30.4/13.4, Jun 29.9/29.0, Jul 28.9/33.1, Aug 28.7/33.4, Sep 28.9/25.3, Oct 27.6/12.7, Nov 23.4/2.7, Dec 19.7/0.4.)

Answer

A line and bar graph (climograph) is suitable — rainfall as bars (left Y-axis) and temperature as a line (right Y-axis), months on the X-axis.

Interpretation: temperature is highest in May (30.4 °C) and lowest in January (19.6 °C); rainfall is concentrated in June–September (maximum 33.4 cm in August) due to the south-west monsoon; winter months are almost dry. Total annual rainfall ≈ 162.5 cm.

A line and bar graph is drawn with rainfall as bars and temperature as a line on a second axis. It shows maximum temperature in May (30.4 °C), minimum in January (19.6 °C), and monsoon rainfall concentrated in June–September (peak 33.4 cm in August), with an annual total of about 162.5 cm.

Topic checklist

• ☒ Line graphs and polygraphs (Q 1 (ii), 1 (iii), activity 1)
• ☒ Bar diagrams, pie diagrams, climograph (Q 2 (ii), 2 (vii), activities 2–5)
• ☒ Thematic maps — dot, choropleth, isopleth, flow (Q 1 (i), 1 (iv), 2 (i), 2 (iii)–(vi), activity 4)

Total questions answered: 16 of 16