Page 253 - ICSE Math 7

Example 5: The runs scored by Rohan in 20 matches are given below. Form a frequency distribution
table and hence calculate his average score.
33, 0, 17, 25, 20, 0, 17, 80, 51, 25, 33, 20, 17, 25, 33, 80, 51, 17, 17, 33

Solution: Runs (x ) Tally marks Frequency (f ) x × f i
i
i
i
0 || 2 0 × 2 = 0
17 5 17 × 5 = 85
20 || 2 20 × 2 = 40
25 ||| 3 25 × 3 = 75

33 || || 4 33 × 4 = 132
51 || 2 51 × 2 = 102
80 || 2 80 × 2 = 160

Total 20 594

x f + x f + x f + ... + x f
Mean = 1 1 2 2 3 3 n n
f + f + f + ... + f n
3
2
1
0 + 85 + 40 + 75 + 132 + 102 + 160 594
= = = 29.7
20 20
Example 6: Organize the marks scored in a class test in the form of a frequency table and find its
arithmetic mean.
7, 6, 4, 2, 5, 3, 5, 4, 5, 2, 7, 6, 2, 8, 5, 6, 9, 5, 3, 6

Solution: Marks (x ) Tally marks Frequency (f ) x × f i
i
i
i
2 3 6
3 2 6

4 2 8
5 5 25

6 4 24
7 2 14

8 1 8
9 1 9

20 100
∑x f 100
Thus, Arithmetic Mean = ∑f i i = 20 = 5 marks.
i
Example 7: The weights of 25 students are given in the following table.

Weight in kg 25 27 28 30 32 33
Number of students 5 4 5 6 3 2

Find the mean weight.

239