The mean of $100$ observations is $50$. If one of the observations which was $50$ is replaced by $150$,the resulting mean will be:

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 mean marks (out of $100$) of boys and girls in an examination are $70$ and $73$,respectively. If the mean marks of all the students in that examination is $71$,find the ratio of the number of boys to the number of girls.

The marks obtained (out of $100$ marks) by $50$ students in a mathematics test are as given below:
$\begin{array}{lrrrrrrrrr} 10, & 65, & 75, & 37, & 8, & 58, & 35, & 42, & 29, & 52 \\ 19, & 52, & 23, & 61, & 88, & 65, & 18, & 77, & 85, & 49, \\ 12, & 7, & 41, & 75, & 52, & 90, & 30, & 89, & 95, & 62, \\ 16, & 61, & 35, & 68, & 22, & 72, & 56, & 27, & 62, & 93, \\ 25, & 59, & 48, & 81, & 26, & 84, & 60, & 39, & 76, & 50 \end{array}$
Represent the data given above by a grouped frequency distribution table,taking the class intervals as $0-10, 10-20, \dots$ etc.

Find the mode of the following observations: $14, 25, 28, 29, 17, 14, 19, 22, 14, 30, 16, 28, 14, 25$.

The mean of $10$ observations is $52$. If $12$ is subtracted from each observation,then the mean of the new observations so obtained is: