The width of the class $50.5-55.5$ is .............

The frequency distribution of the marks scored by $35$ students in a $60$ marks test is as below:

Marks scored	No. of students
$0-10$	$2$
$10-20$	$7$
$20-30$	$8$
$30-40$	$7$
$40-50$	$8$
$50-60$	$3$

Represent the data by a histogram.

The mean of five numbers is $30$. If one number is excluded,their mean becomes $28$. The excluded number is:

The mean of the $10$ observations is $68$. If each observation is divided by $2$ and then $6$ is added to each result, find the mean of the new observations so obtained.

The facts or figures,which are numerical or otherwise,collected with a definite purpose are called .......

The class marks of a continuous distribution are: $1.04, 1.14, 1.24, 1.34, 1.44, 1.54$ and $1.64$. Is it correct to say that the last interval will be $1.55-1.73$? Justify your answer.