The following table shows the marks obtained by 6 students in a class. Find the average marks of the students in the class.

$\begin{matrix} M a r k s & F r e q u e n c y 78 & 2 65 & 1 85 & 2 74 & 1 \end{matrix}$

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Solution

The total marks obtained by 6 students of the class are 156 + 65 + 170 + 74 = 465

Now, the mean or average value of marks can be calculated by dividing the summation of marks obtained by each student

Mean = $\frac{S u m o f o b s e r v a t i o n s}{N o . o f O b s e r v a t i o n s}$

= $\frac{465}{6}$ = 77.5

$\begin{matrix} M a r k s (x_{i}) & F r e q u e n c y (f_{i}) & x_{i} f_{i} 78 & 2 & 156 65 & 1 & 65 85 & 2 & 170 74 & 1 & 74 T o t a l & \sum f_{i} = 6 & \sum x_{i} f_{i} = 465 \end{matrix}$

So, mean or average = $\frac{\sum x_{i} f_{i}}{\sum f_{i}}$ = $\frac{465}{6}$ = 77.5

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Similar questions

Find the mean of the marks obtained by 20 students in a classroom.

$\begin{matrix} Marks & Frequency 87 & 2 78 & 3 53 & 1 98 & 2 92 & 2 97 & 1 81 & 2 65 & 2 98 & 3 76 & 2 \end{matrix}$

Marks (mid-points)	45	55	65	75	85
No. of Students	5	9	12	8	2

Marks (Class interval)	Number of students (Frequency)
1−10	7
11−20	10
21−30	6
31−40	4
41−50	3

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