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Mathematics · 2022 · 2 marks
CBSE 2022 · Region 4 · Set 2 · Q6
If the mean of the following frequency distribution is $\displaystyle 18$, then find the missing frequency ' f '. Class $\displaystyle 11$-$\displaystyle 13$ $\displaystyle 13$-$\displaystyle 15$ $\displaystyle 15$-$\displaystyle 17$ $\displaystyle 17$-$\displaystyle 19$ $\displaystyle 19$-$\displaystyle 21$ $\displaystyle 21$-$\displaystyle 23$ $\displaystyle 23$-$\displaystyle 25$ Frequency $\displaystyle 3$ $\displaystyle 6$ $\displaystyle 9$ $\displaystyle 13$ f $\displaystyle 5$ $\displaystyle 4$
| Class | $\displaystyle 11$-$\displaystyle 13$ | $\displaystyle 13$-$\displaystyle 15$ | $\displaystyle 15$-$\displaystyle 17$ | $\displaystyle 17$-$\displaystyle 19$ | $\displaystyle 19$-$\displaystyle 21$ | $\displaystyle 21$-$\displaystyle 23$ | $\displaystyle 23$-$\displaystyle 25$ |
| Frequency | $\displaystyle 3$ | $\displaystyle 6$ | $\displaystyle 9$ | $\displaystyle 13$ | f | $\displaystyle 5$ | $\displaystyle 4$ |
Marking-scheme solution
| Class Interval | \(\displaystyle x_{i}\) | \(\displaystyle f_{i}\) | \(\displaystyle x_{i} f_{i}\) |
| $\displaystyle 11$-$\displaystyle 13$ | $\displaystyle 12$ | $\displaystyle 3$ | $\displaystyle 36$ |
| $\displaystyle 13$-$\displaystyle 15$ | $\displaystyle 14$ | $\displaystyle 6$ | $\displaystyle 84$ |
| $\displaystyle 15$-$\displaystyle 17$ | $\displaystyle 16$ | $\displaystyle 9$ | $\displaystyle 144$ |
| $\displaystyle 17$-$\displaystyle 19$ | $\displaystyle 18$ | $\displaystyle 13$ | $\displaystyle 234$ |
| $\displaystyle 19$-$\displaystyle 21$ | $\displaystyle 20$ | \(\displaystyle f\) | \(\displaystyle 20 f\) |
| $\displaystyle 21$-$\displaystyle 23$ | $\displaystyle 22$ | $\displaystyle 5$ | $\displaystyle 110$ |
| $\displaystyle 23$-$\displaystyle 25$ | $\displaystyle 24$ | $\displaystyle 4$ | $\displaystyle 96$ |
| \(\displaystyle 40+f\) | \(\displaystyle 704+20 f\) |
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CBSE Class 10 Mathematics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.