NCERT Solutions For Class 12 Geography Part C Chapter 3 Graphical Representation of Data

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    46. Choose the right answer from the four alternatives given below:

    (i) Which one of the following map shows the population distribution:

    • (a) Choropleth maps
    • (b) Isopleth maps
    • (c) Dot maps
    • (d) Square root maps
    • Ans. (c) Dot maps

    (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
    • Ans. (a) Line graph

    (iii) Polygraph is constructed to represent:

    • (a) Only one variable
    • (b) Two variables only
    • (c) More than two variables
    • (d) None of the above
    • Ans. (c) More than two variables
    (iv) Which one of the following maps is known as “Dynamic Map”?
    • (a) Dot map
    • (b) Choropleth
    • (c) Isopleth
    • (d) Flow map
    • Ans. (d) Flow map

    47. Answer the following questions in about 30 words:

    (i) What is a thematic map?

    Ans. A thematic map is a map constructed to examine a specific topic such as rainfall, temperature, soil type, and so on. Thematic maps, graphs, and diagrams are useful for comparing internal changes within the data of various attributes.

    (ii) Differentiate between multiple bar diagram and compound bar diagram.

    Ans. Multiple Bar Diagram: For the purpose of comparison, multiple bar diagrams are used to represent two or more variables. For example, we may draw two bars, one for male literacy and the other for female literacy.

    A compound bar diagram shows distinct components when they are grouped into one set of variables or when different components of one component are combined. Distinct variables are displayed in a single bar with different rectangles in this manner. For example, India’s entire energy generation is classified into hydropower, thermal power, nuclear power, etc.

    (iii) What are the requirements to construct a dot map?

    Ans. Requirements are as follow:

    1. A map of the given area’s administrative borders, including state, district, and block boundaries.
    2. Statistical data on a certain issue for the administrative units chosen, such as total population, livestock, and so on.
    3. A scale is used to determine the value of a dot.
    4. Relief and drainage maps, as well as a physiographic map of the region.


    1. The lines that demarcate the boundaries of several administrative divisions should be thin and faint.
    2. The size of all the dots should be the same.

    (iv) Describe the method of constructing a traffic flow map.

    Ans. A flow chart is a blend of a graph and a map. It is drawn to depict the delivery of resources or people between origin and destination points. It’s also known as Dynamic Map. Lines of proportionate width are used to create these graphs.

    Methods for Creating a Traffic Flow Diagram:

    1. A route map depicting the desired transport routes along with the connecting stations.
    2. The data about the flow of goods, services, number of vehicles, etc., along with the movement’s point of origin and destination.
    3. The selection of a scale through which the data related to the number of passengers and goods or the number of vehicles is to be represented.

    (v) What is an Isopleth map ? How an interpolation is carried out ?

    Ans. In the form of quantity, intensity, and density, isopleths are imaginary lines of equal value. The words isos and plethron signify equal and measure, respectively. Isopleths are such lines of equal value. These lines run through all of the sites with similar values. The more frequently drawn isopleths include Isotherm (equal temperature), Isobar (equal pressure), Isohyets (equal rainfall), Isonephs (equal cloudiness), Isohels (equal sunshine), contours (equal heights), Isobaths (equal depths), Isohaline (equal salinity), etc. Interpolation is a technique for inserting intermediate values between the observed values of two stations/locations, such as the temperature measured in Chennai and Hyderabad or the spot heights of two places. Interpolation is the process of drawing isopleths to connect sites with the same value. 

    Interpolation Techniques:

    1. To begin, identify the map’s minimum and maximum values.
    2. Calculate the value range equal to the highest value minus the minimum value.
    3. Based on the range, determine the interval in a whole number, such as 5, 10, 15, etc.
    4. The following formula is used to identify the exact spot where an isopleth should be drawn.

    Point of isopleth

    $$=\frac{\text{Disance between two points in (cm)}}{\text{Difference between the two values}} × \text{Interval of corresponding points}$$

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

    Ans. Steps to be followed to draw a choropleth map are:

    1. Sort the information ascending or descending.
    2. To indicate extremely high, high, medium, low, and very low concentrations, divide the data into five groups.
    3. Range/5 and Range = highest value – minimum value are two formulas for determining the gap between the categories.
    4. The patterns, hues, or colours that will be used to represent the various categories should be labelled in ascending or descending order. 

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

    Ans. Steps to be followed:

    1. Arrange the data in ascending order.
    2. Calculate the degree of angles showing in the given values.
    3. Plot the data dividing the circle into the required number of divisions.
    4. Select the suitable radius for the circle to be drawn.
    5. Draw the line from the centre of the circle to the arc as a radius.
    6. Measure the angles from the arc of the circle for each category of vehicle in an ascending order clockwise, starting with smaller angles.

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