$A$ school has four sections of chemistry in class $XII$ having $40, 35, 45$ and $42$ students. The mean marks obtained in chemistry test are $50, 60, 55$ and $45$ respectively for the four sections. The overall average of marks per student is:
- A$53$
- B$45$
- C$55.3$
- D$52.25$
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If for some positive $x \in R$,the frequency distribution of the marks obtained by $20$ students in a certain test is as follows:
Marks $2$ $3$ $5$ $7$ Frequency $(x+1)^2$ $2x-5$ $x^2-3x$ $x$
Then the mean of the marks is:
| Marks | $2$ | $3$ | $5$ | $7$ |
|---|---|---|---|---|
| Frequency | $(x+1)^2$ | $2x-5$ | $x^2-3x$ | $x$ |
Then the mean of the marks is:
If the values $1, \frac{1}{2}, \frac{1}{3}, \dots, \frac{1}{n}$ have frequencies $1, 2, 3, \dots, n$ respectively,what is their mean?
Medium
View SolutionThe arithmetic mean of the first $n$ natural numbers is:
Easy
View SolutionWhich of the following,in the case of discrete data,is not equal to the median?
If the values $1, \frac{1}{2}, \frac{1}{3}, \frac{1}{4}, \frac{1}{5}, \dots, \frac{1}{n}$ occur at frequencies $1, 2, 3, 4, 5, \dots, n$ in a distribution,then the mean is
Medium
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