The average weight of a group of $20$ boys was calculated to be $89.4 \, kg$ and it was later discovered that one weight was misread as $78 \, kg$ instead of $87 \, kg$. The correct average weight is (in $kg$).

The average of ten numbers is calculated. If each number is increased by $12 \%$,then the average

The average speed of a train running at a speed of $30 \, km/h$ during the first $100 \, km$,at $40 \, km/h$ during the second $100 \, km$,and at $50 \, km/h$ during the last $100 \, km$ is nearly (in $km/h$):

If the mean of $5$ observations $x, x+2, x+4, x+6$ and $x+8$ is $11,$ then the mean of the last three observations is

The average age of Donald,his wife,and their two children is $23 \text{ years}$. His wife is $4 \text{ years}$ younger than Donald,and his wife was $24 \text{ years}$ old when his daughter was born. He was $32 \text{ years}$ old when his son was born. What is the average age of Donald and his daughter? (in $\text{years}$)

The mean of $19$ observations is $4$. If one more observation of $24$ is added to the data,the new mean will be