Page 255 - ICSE Math 7

Suppose the weights of 20 students of class VII in kg are as follows:
33, 30, 35, 28, 30, 35, 42, 35, 32, 35, 38, 35, 28, 40, 42, 31, 39, 35, 28, 40
Since the data is large, we convert it into frequency table.

Weight Tally marks f Weight Tally marks f

28 3 35 6

30 2 38 1

31 1 39 1

32 1 40 2

33 1 42 2

Clearly the maximum frequency 6 corresponds to the weight 35 kg. Hence, the modal weight is
35 kg. It means the maximum number of students in the class weigh 35 kg.
Example 9: Marks scored by 7 students in a test are: 37, 15, 40, 30, 58, 25, 40.

Find the range, mean, median and mode of the data.
Solution: We first arrange the data in ascending order as: 15, 25, 30, 37, 40, 40, 58
(i) Range = Largest value – smallest value = 58 – 15 = 43

Sum of the observations 245
(ii) Mean = = = 35
Tota umber of observations 7

n + 1 7 + 1
(iii) Median = th term = th term = 4th term
2 2
Thus, the value of the middlemost term = 37
(iv) Mode = The value which occurs the maximum number of times = 40

Example 10: Roy is incharge of a hostel mess. He has to decide upon the number of chapattis needed
for 25 students every day. Suppose the students eat the following number of chapattis:
2, 3, 2, 3, 2, 1, 2, 3, 2, 2, 5, 3, 4, 2, 4, 2, 3, 2, 4, 4, 2, 3, 2, 2, 4

Find the mean, median and mode of the data. Which of the three is the most appropriate
representative value of the data? Justify.

Solution: Since the number of observations is large, we convert the data into frequency table.

Number of chapattis (x) Tally bars f

1 1

2 12

3 6

4 5

5 1

241