Class 7 Maths Chapter 3 Data Handling Exercise 3.2 pdf notes:-

**Exercise 3.2** Class 7 maths Chapter 3 Pdf Notes:-

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## Ncert Solution for Class 7 Maths Chapter 3 Data Handling Exercise 3.2 Tips:-

**ARITHMETIC MEAN**

The most common representative value of a group of data is the arithmetic mean or the

mean. To understand this in a better way, let us look at the following example:

Two vessels contain 20 litres and 60 litres of milk respectively. What is the amount that

each vessel would have, if both share the milk equally? When we ask this question we are

seeking the arithmetic mean.

MODE

As we have said Mean is not the only measure of central tendency or the only form of

representative value. For different requirements from a data, other measures of central

tendencies are used.

Look at the following example

To find out the weekly demand for different sizes of shirt, a shopkeeper kept records of sales

of sizes 90 cm, 95 cm, 100 cm, 105 cm, 110 cm. Following is the record for a week:

Size (in inches) 90 cm 95 cm 100 cm 105 cm 110 cm Total

Number of Shirts Sold 8 22 32 37 6 105

If he found the mean number of shirts sold, do you think that he would be able to

decide which shirt sizes to keep in stock?

Mean of total shirts sold =

Total number of shirts sold

Number of different sizes of shirts = = 105

5

21

Should he obtain 21 shirts of each size? If he does so, will he be able to cater to the

needs of the customers?

The shopkeeper, on looking at the record, decides to procure shirts of sizes 95 cm,

100 cm, 105 cm. He decided to postpone the procurement of the shirts of other sizes

because of their small number of buyers.

Look at another example

The owner of a readymade dress shop says, āThe most popular size of dress I sell is the

size 90 cm.

Observe that here also, the owner is concerned about the number

of shirts of different sizes sold. She is however looking at the shirt size

that is sold the most. This is another representative value for the data.

The highest occuring event is the sale of size 90 cm.This representative

value is called the mode of the data.

The mode of a set of observations is the observation that occurs

most often.

EXAMPLE 4 Find the mode of the given set of numbers: 1, 1, 2, 4, 3, 2, 1, 2, 2, 4

SOLUTION Arranging the numbers with same values together, we get

1, 1, 1, 2, 2, 2, 2, 3, 4, 4

Mode of this data is 2 because it occurs more frequently than other observations.

3.6.1 Mode of Large Data

Putting the same observations together and counting them is not easy if the number of

observations is large. In such cases we tabulate the data. Tabulation can begin by putting

tally marks and finding the frequency, as you did in your previous class.