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प्रश्न
Construct a frequency polygon for the following data:
| Class-Intervals | 10 - 14 | 15 - 19 | 20 - 24 | 25 - 29 | 30 - 34 |
| Frequency | 5 | 8 | 12 | 9 | 4 |
उत्तर
The class intervals are inclusive. We will first convert them into the exclusive form.
| Class-Interval | Frequency |
| 9.5 - 14.5 | 5 |
| 14.5 - 19.5 | 8 |
| 19.5 - 24.5 | 12 |
| 24.5 - 29.5 | 9 |
| 29.5 - 34.5 | 4 |
Steps:
- Draw a histogram for the given data.
- Mark the mid-point at the top of each rectangle of the histogram drawn.
- Also, mark the mid-point of the immediately lower class-interval and mid-point of the immediately higher class-interval.
- Join the consecutive mid-points marked by straight lines to obtain the required frequency polygon.
The required frequency polygon is as follows:
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संबंधित प्रश्न
The following data on the number of girls (to the nearest ten) per thousand boys in different sections of Indian society is given below.
| Section | Number of girls per thousand boys |
| Scheduled Caste (SC) | 940 |
| Scheduled Tribe (ST) | 970 |
| Non SC/ST | 920 |
| Backward districts | 950 |
| Non-backward districts | 920 |
| Rural | 930 |
| Urban | 910 |
- Represent the information above by a bar graph.
- In the classroom discuss what conclusions can be arrived at from the graph.
The following table gives the distribution of students of two sections according to the mark obtained by them:-
| Section A | Section B | ||
| Marks | Frequency | Marks | Frequency |
| 0 - 10 | 3 | 0 - 10 | 5 |
| 10 - 20 | 9 | 10 - 20 | 19 |
| 20 - 30 | 17 | 20 - 30 | 15 |
| 30 - 40 | 12 | 30 - 40 | 10 |
| 40 - 50 | 9 | 40 - 50 | 1 |
Represent the marks of the students of both the sections on the same graph by two frequency polygons. From the two polygons compare the performance of the two sections.
Given below (Fig. below) is the bar graph indicating the marks obtained out of 50 in mathematics paper by 100 students. Read the bar graph and answer the following questions:
(i) It is decided to distribute work books on mathematics to the students obtaining less than 20 marks, giving one workbook to each of such students. If a work book
costs Rs 5, what sum is required to buy the work books?
(ii) Every student belonging to the highest mark group is entitled to get a prize of Rs. 10. How much amount of money is required for distributing the prize money?
(iii) Every student belonging to the lowest mark—group has to solve 5 problems per day. How many problems, in all, will be solved by the students of this group per day?
(iv) State whether true or false.
a. 17% students have obtained marks ranging from 40 to 49.
b. 59 students have obtained marks ranging from 10 to 29.
(v) What is the number of students getting less than 20 marks?
(vi) What is the number of students getting more than 29 marks?
(vii) What is the number of students getting marks between 9 and 40?
(viii) What is the number of students belonging to the highest mark group?
(ix) What is the number of students obtaining more than 19 marks?
Read the following bar graph(Fig. 23.15) and answer the following questions:
(i) What information is given by the bar graph?
(ii) What was the production of a student in the year 1980 - 81?
(iii) What is the minimum and maximum productions of cement and corresponding years?
Read the bar graph given in Fig. below and answer the following questions:
(i) What information does it give?
(ii) In which part the expenditure on education is maximum in 1980?
(iii) In which part the expenditure has gone up from 1980 to 1990?
(iv) In which part the gap between 1980 and 1990 is maximum?
The production of saleable steel in some of the steel plants our country during 1999 is given below:
| Plant | Bhilai | Durgapur | Rourkela | Bokaro |
| Production (In thousand tonnes) |
160 | 80 | 200 | 150 |
Construct a bar graph to represent the above data on a graph paper by using the scale 1 big divisions = 20 thousand tonnes.
A frequency polygon is constructed by plotting frequency of the class interval and the
Mr. Mirza’s monthly income is Rs. 7,200. He spends Rs. 1,800 on rent, Rs. 2,700 on food, Rs. 900 on the education of his children; Rs. 1,200 on Other things and saves the rest.
Draw a pie-chart to represent it.
Draw a histogram to represent the following grouped frequency distribution:
| Ages (in years) | Number of teachers |
| 20 – 24 | 10 |
| 25 – 29 | 28 |
| 30 – 34 | 32 |
| 35 – 39 | 48 |
| 40 – 44 | 50 |
| 45 – 49 | 35 |
| 50 – 54 | 12 |
Following table gives the distribution of students of sections A and B of a class according to the marks obtained by them.
| Section A | Section B | ||
| Marks | Frequency | Marks | Frequency |
| 0 – 15 | 5 | 0 – 15 | 3 |
| 15 – 30 | 12 | 15 – 30 | 16 |
| 30 – 45 | 28 | 30 – 45 | 25 |
| 45 – 60 | 30 | 45 – 60 | 27 |
| 60 –75 | 35 | 60 – 75 | 40 |
| 75 – 90 | 13 | 75 – 90 | 10 |
Represent the marks of the students of both the sections on the same graph by two frequency polygons. What do you observe?
