B Nirmala Shastry solutions for Mathematics [English] Class 9 ICSE chapter 15 - Statistics [Latest edition]

The following are ages of 30 children, in years, from a pre-primary school. Prepare an ungrouped frequency distribution table.

The following are the number of children in each of 30 families in a housing society. Prepare an ungrouped frequency distribution table.

The marks scored in a test by 40 students of a class are recorded below:

Prepare a grouped frequency distribution table taking classes 21- 30, 31 - 40, ...

Ages of 27 members of a club are given below in years:

Prepare a grouped frequency distribution table taking classes 20 - 30, 30 - 40, ...

The students of a school collected certain amount of money for the Home for the aged. The amounts are given below in rupees. Make a frequency distribution table with classes 100 - 200, 200 - 300, ...

The consumption of electricity (in units) for one month of 36 houses in a colony are given below:

Construct a grouped frequency distribution table by taking classes 50 - 60, 60 - 70, ...

The weights of 40 students of class 9 of a school are given below (in kg). Make a grouped frequency distribution table by taking classes 35 - 45, 45 - 55, ...

Prepare a frequency distribution table from the following:

Construct a cumulative frequency table from the following frequency distribution.

Rani reads a few pages of a novel everyday. She reads the following number of pages per day in a week.

23, 26, 21, 19, 37, 18, 24

1. Find the mean number of pages read by her.
2. Also find the median.

Following are the ages of 9 children in a group. Find their (i) mean, (ii) median.

13, 10, 9, 11, 12, 14, 12, 15, 12

The daily consumption of milk in litres by 10 families in a colony are given below:

3.5, 3, 2, 2.5, 4, 3, 1, 5, 3.5, 1.5

Find their mean and median.

The number of students in different years of a secondary school are given below:

124, 146, 156, 148, 160, 136

Find their mean and median.

The weights of 5 children in a group (in kg) are 25, 35, 35, 28 and 32. Find their mean weight and median weight. After a year it was found that they all gained 3 kg each. Find the new mean weight.

The following numbers are arranged in ascending order: 2, 3, x, y, 7, 9, 12, 14. If their median is 6 and mean is 7, find x and y.

Find the mean and median of the following:

11, 14, 15, 14, 17, 19

If another number x is added to the given numbers, the new mean is 14. Find the value of x.

Alia is 9 years older than her twin brothers. If they are x years old, find the mean age of the three children in simplest terms.

Mean of 6, 4, 3, 5, 4, 2 is m and median of 0, 3, 2, m, 5 is n. Find m and n.

The mean marks of 30 students of a class is 70. Find the marks of the topper if the mean marks of the others is 69.

The mean marks of 20 students is 62. It was later discovered that one of the students marks were written wrongly as 86 instead of 68. Find the correct mean.

The mean weight of 5 students is 47 kg. If four of them weigh 44 kg, 45 kg, 47 kg and 49 kg. Find the weight of the fifth student.

The mean height of 8 students is 152 cm. Three more students of heights 160 cm, 165 cm, and 164 cm join the group. Find the new mean height.

The mean marks of 8 girls in a class test is 52 and the mean marks of 12 boys of the same class in the same test is 51. Find the mean marks of all the 20 students in the class.

The following numbers arranged in ascending order have their mean and median same. 4, 4, x − 2, x + 1, x + 3, 12, 13. Find the value of x and the median.

The following numbers are arranged in ascending order. Find x and the mean if their median is 10.

4, 7, x + 1, x + 5, 15, 20

Mean temperature of a city in a certain week is 30°C. If the mean temperature of first 3 days of the week is 32°C, what is the mean temperature of last 4 days of the week?

The mean weight of 6 children is 35 kg. When a new boy joined the group, the mean weight becomes 36 kg. What is the weight of the new boy?

The mean age of 9 children in a class is 15 years. When the teacher’s age is included, the mean age becomes 18 years. Find the teacher’s age.

The following are class mark, of a frequency distribution 12, 16, 20, 24, 28. Give the class.

The mean of 3, 7, 5, 8, 7 is ______.

The median of 6, 4, 14, 9, 5, 3, 8 is ______.

The median of 19, 12, 10, 15, 13, 21 is ______.

The mean and median of the data are same. If the numbers are arranged in ascending order, the value of x is 3, 5, x, 9, 11.

The following numbers are arranged in ascending order: 10, 17, x − 2, x + 1, x + 4, 27, 30. Their median is 21 ∴ The value of x is ______.

Mean of 8, 4, 3, 5, 4, 6 is m and median of 0, 3, 2, m, 5 is n.

The value of m is:

Mean of 8, 4, 3, 5, 4, 6 is m and median of 0, 3, 2, m, 5 is n.

The value of n is:

In the classes 0-9, 10-19, 20-29, ....., the class size is ______.

When the largest number in the given data is increased by 10 and the smallest number is decreased by 5, the median increases by ______.

When the class intervals are 40-50, 50-60, 60-70 etc. The number 60 is included in the class is ______.

In a group of children, the mean marks of 4 boys is 80 and the mean marks of 6 girls is 85. The mean marks of the whole group is ______.

The mean weight of 10 boys is 50 kg. When one boy left, the mean weight becomes 49 kg. The weight of that boy is ______.

If each student of a class of 10 students was given 5 marks more in an exam, the mean marks ______.

To draw a frequency polygon, points with y-coordinates as frequencies are plotted against the ______.

To compare two different sets of data of same kind we can use ______ on the group.

Assertion (A): A group of 7 children’s ages in years are 8, 9, 11, 6, 7, 12, 14. Their median age is 6 years.

Reason (R): Median is the middle number in the arranged group.

Assertion (A): Mean and median are always one of the numbers of the observation.

Reason (R): Mean and median are measures representing the data which need not be one of the observations.

Assertion (A): When class intervals are 10 - 20, 20 - 30, 30 - 40 etc, 30 is included in 30 - 40 class.

Reason (R): In 20 - 30 all values from 20 - 29 are included.

Assertion (A): When the mean age of 20 children is 10 years and the mean age of 10 other children is 13 years, then the mean age of 30 children is 11 years.

Reason (R): Mean of 30 children = `"Total age of 20 + Total age of 10"/30`

Assertion (A): Number of members in a family is an example of discrete data whereas their heights and weights form continuous data.

Reason (R): Discrete data can be in whole numbers while continuous data can take any value within a range.

Prepare a frequency distribution table for the following, using class intervals 0 - 9, 10 - 19, ...

23, 38, 40, 57, 74, 31, 47, 52, 56, 59, 44, 56, 18, 46, 63, 57, 79, 39, 39, 20, 39, 45, 49, 60, 32, 47, 19, 69, 20, 5, 8, 53, 28, 48, 73, 77, 63, 52, 65, 11

Find the mean and median for the following:

3, 7, 12, 5, 8, 14, 7

Find the mean and median for the following:

11, 5, 2, 8, 4, 5, 7, 9, 1, 12

The following numbers are pre-arranged in ascending order. Their median is 12. Find the value of x and their mean.

6, 9, x, x + 2, x + 3, 19

The mean and median of the following are same. Find the value of x if the numbers are arranged in ascending order.

1, 3, 4, x, 10, 15, 21

Ten students collected the following amounts (in rupees) for an orphanage:

250, 450, 500, 750, 300, 650, 200, 350, 500, 650

Find their mean and median.

The mean temperature of a town in a week in summer is 36°C. If the mean temperature of first 4 days of the week is 35°C and that of Saturday and Sunday is 37°C. Find the temperature on Friday.

Construct a cumulative frequency distribution table for the following:

The mean age of A and B is 14 years, the mean age of B and C is 17 years and the mean age of A and C is 15 years. Find the ages of A, B and C.