# RS Aggarwal Solutions Class 9 Mathematics Solutions for Mean Median And Mode Of Ungrouped Data Exercise 18B in Chapter 18 - Mean Median And Mode Of Ungrouped Data

Question 7 Mean Median And Mode Of Ungrouped Data Exercise 18B

If the mean of the following data is 20.2, find the value of p.

Variable (xi) Frequency (fi)
10 6
15 8
20 p
25 10
30 6

The mean is the average or computed centre value of a set of numbers used to determine the data's central tendency. The statistical measure of central tendency is a single value that represents the full collection of data or distribution.

Variable (xi) Frequency (fi) fi xi
10 6 60
15 8 120
20 p 20p
25 10 250
30 6 180
Σ fi = 30 + p Σ fi xi = 610 + 20p

It is given that

Mean = 20.2

We know that

Mean = Σ fi xi/ Σ fi

So we get

(610 + 20p)/ (30 + p) = 20.2

On further calculation

610 + 20p = 606 + 20.2p

So we get

0.2p = 4

By division

p = 20

Therefore, the value of p is 20.

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