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.
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Measures of Central Tendency
21. The stem-and-leaf diagram on the right shows a set of data.
(a) Find the mean of the set of data.
Leaf (1)
(b) Find the median of the set of data.
(c) Find the mode of the set of data.
22. An organization conducts a survey about the obesity of students. The following stem-and-leaf diagram
shows the body mass index (BMI) distribution of obese students in this survey.
BMI distribution
Stem (10 kg/m
2
) Leaf (1 kg/m
2
)
2
3
4
6 6 6 6 7 7
1 1 2 2 2 3 3 4 4 7 8
0 0 1
Find the median and the mode of the body mass indices of the students in this survey.
23. The following stem-and-leaf diagram shows
the weights of some pencils.
Stem (1 g) Leaf (0.1 g)
6
7
8
3 a a a
1 2 2 3 b
0 c 5 5
The mean, the median and the mode of the weights of the pencils are 7.5 g, 7.35 g and 6.5 g
respectively. Find the values of a , b and
24. Consider the set of data: a , a + 2, b , b , c , where a , b and c are distinct. If the mean, the median and the
mode of the set of data are 12.6, 13 and 14 respectively, find the values of a , b and
7 7 7
8 9 9 9 9
1 3
7
6 8
8 9
c .
c .
Multiple Choice Questions
25. If the mode of nine numbers 3, 2, 2, 4, 5, 9, 7, x and y is 3, then the median of the nine numbers is
Stem (10) Leaf (1)
3
4
5
3 6 7
1 1 6 8
7 8 8
26. If the mean of six numbers 25, 14, 27, 24, 10 and x is x , then the median of the six numbers is
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Book 3A Chapter 6
C. 21.
D. 22.
86 © Educational Publishing House Ltd

Measures of Central Tendency
6.2 Measures of Central Tendency for Data Organized by Frequency Distribution Tables
Demonstration 1
The following table shows the numbers of pens
owned by 30 students.
Number of pens 0 1 2 3 4
Frequency 2 9 13 5 1
Find the mean number of pens owned by the
students.
1. The following table shows the numbers of
medals won by 25 athletes in a sports
day.
Number of medals 0 1 2 3 4
Frequency 5 8 1 7 4
Find the mean number of medals won by the
athletes.
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