The average of four consecutive odd numbers is $40 .$ What is the largest number?
$42$
$45$
$43$
$44$
Find average of all prime numbers between $60$ and $90.$
The average age of a man and his two twin born on the same day is $30 \,year.$ The ratio of the ages of father and one son is $5: 2,$ what is the father's age in $year?$
The mean of $100$ items was $46 .$ Later on, it was discovered that an item $16$ was misread as $61$ and another item $43$ was misread as $34.$ It was also found that the number of items was $90$ and not $100 .$ Then, what is the correct mean?
A group of boys has an average weight of $36 \,kg$. One boy weighing $42 \,kg$ leaves the group and another boy weighing $30\, kg$ joints the group. If the average now becomes $35.7\, kg$, then how many boys are there in the group?
The average age of a class of $30$ students and a teacher reduce by $0.5 \,years$ if we exclude the teacher. If the initial average is $14 \,years,$ find the age of the class teacher in $year$ ?