Find the number of observations,if the sum of some observations is $975$ and their mean is $32.5$.

Draw a frequency polygon for the following frequency distribution:

Class	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$	$70-80$
Frequency	$5$	$7$	$12$	$7$	$10$	$9$

The blood groups of $30$ students are recorded as follows:
$A, B, O, A, AB, O, A, O, B, A, O, B, A, AB, B, A, AB, B$
$A, A, O, A, AB, B, A, O, B, A, B, A$
Prepare a frequency distribution table for the data.

The observations $7, 15, x-1, x+1, 24, 28$ have been arranged in ascending order. If the median of the data is $21$,find the value of $x$.

$A$ football player scored the following number of goals in $10$ matches:
$1, 3, 2, 5, 8, 6, 1, 4, 7, 9$
Since the number of matches is $10$ (an even number),the median is calculated as:
Median $= \frac{5^{\text{th}} \text{ observation} + 6^{\text{th}} \text{ observation}}{2}$
$= \frac{8 + 6}{2} = 7$
Is this the correct answer? If not,why?

To draw a histogram to represent the following frequency distribution:

Class interval	$5-10$	$10-15$	$15-25$	$25-45$	$45-75$
Frequency	$6$	$12$	$10$	$8$	$15$

The adjusted frequency for the class $25-45$ is: