Page 322 - Start Up Mathematics_8 (Non CCE)

EXERCISE 20.2

1. The frequency distribution of weights (in kg) of 35 persons Weight Tally Frequency
is given in the table: (in kg) marks
(a) What is the lower limit of the class 50–55? 40–45 5
7
45–50
(b) What is the class size of the intervals? 50–55 | | | 11
(c) What is the upper limit of class 55–60?
55–60 | | 7
(d) Find the class marks of the classes 45–50 and 55–60. 60–65 5

(e) What is the frequency of the class interval 40–45? Total 35
2. Following are the weights (in kg) of 20 boys of a class. Group
the data into classes 40–43, 43–46, etc.
43.0, 49.2, 48.5, 46.0, 47.6, 47.4, 51.0, 53.1, 54.0, 42.5, 40.7, 44.2, 56.3, 37.1, 49.0, 48.1, 40.9, 45.4, 56.4, 53.5
3. The daily earnings of 35 medical stores (in `) are as follows:
Prepare a frequency distribution Daily earnings 61 149 180 181 241 259 310 391
table taking equal class size, with
intervals 50–100 (100 not included). No. of stores 4 7 4 8 5 3 2 2
4. A test was given to a group of 35 students for a job. The time taken (in min) by the students to
complete the test was:
35, 30, 40, 27, 28, 44, 32, 43, 40, 25, 27, 48, 49, 47, 37, 38, 43, 41, 42, 32, 31, 48, 49, 34, 32, 35,
45, 44, 40, 40, 27, 39, 48, 35, 41
Prepare a grouped frequency table for this data taking intervals 25–30, 30–35 and so on.
5. Construct a frequency distribution table of class size 10 for the following data:
22, 11, 28, 15, 10, 7, 5, 21, 35, 42, 31, 29, 16, 24, 25, 12, 10, 18, 11, 14, 6, 3, 8, 11, 23, 25, 33, 45,
16, 49, 35, 14, 9, 22, 11, 15, 27, 30, 19, 8
6. The pulse rate (per min) of 30 persons was recorded as given below:
61, 76, 72, 73, 71, 66, 78, 73, 68, 81, 78, 63, 72, 75, 80, 68, 75, 62, 71, 81, 73, 60, 79, 72, 73, 74,
71, 64, 76, 71
Construct a frequency table using class intervals of equal width, one class interval being
60–65.

Bar Graph (or Column Graph)
A bar graph is a pictorial representation of numerical data in the form of rectangles (or bars) of equal width
and varying heights. These rectangles are drawn either vertically or horizontally, keeping equal space between
them. The height (or length) of a rectangle depends on the numerical value it represents.

Drawing a bar graph
Step 1: Take a graph paper and draw a horizontal line OX and a vertical line OY. These lines are called
the X-axis and the Y-axis respectively.
Step 2: Mark points at equal intervals along the X-axis. Below these points write the names of the data
items whose values are to be plotted.
Step 3: Choose a suitable scale on Y-axis. On that scale find the heights of the bars for the given numerical
values.
Step 4: Mark off these heights parallel to the Y-axis from the points taken in step 2.
Step 5: On the X-axis, draw bars of equal width for the heights marked in step 4. The bars should be
centered on the points marked on the X-axis. These bars represent the given numerical data.

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