A random sample of 20 people is classified in the following table according to their ages:

Age

Frequency

15 – 25

2

25 – 35

4

35 – 45

6

45 – 55

5

55 - 65

3


What is the mean age of this group of people?

This question was previously asked in
NDA (Held On: 18 Sept 2016) Maths Previous Year paper
View all NDA Papers >
  1. 41.0
  2. 41.5
  3. 42.0
  4. 42.5

Answer (Detailed Solution Below)

Option 2 : 41.5
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Detailed Solution

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Concept:

\({\rm{Mean}} = \frac{{\sum {\rm{xf}}}}{{\sum {\rm{f}}}}\)

Calculation:

Age

Frequency (f)

x

xf

15 – 25

2

20

40

25 – 35

4

30

120

35 – 45

6

40

240

45 – 55

5

50

250

55 - 65

3

60

180

 

\(\sum {\rm{f}} = 20\)

 

\(\sum {\rm{xf}} = 830\)

 

We know that, \({\rm{Mean}} = \frac{{\sum {\rm{xf}}}}{{\sum {\rm{f}}}}\)

\(\therefore {\rm{Mean}} = \frac{{830}}{{20}} = 41.5\)

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