The average of four consecutive odd numbers is $40 .$ What is the largest number?

The $average$ of $30$ numbers is $12 .$ The $average$ of the first $20$ of them is $11$ and that of the next $9$ is $10 .$ The last number is

$16$ children are to be divided into two groups $A$ and $B$ of $10$ and $6$ children, respectively. The average marks obtained by the children of group $A$ is $75$ and that of all the children is $76 .$ Then, the average marks of the children of group $B$ is ?

A person travels $\frac{1}{3}$ of his journey by bus at $60\, km / h$ , $\frac{1}{3}$ by scooter at $30\, km / h$ and the rest by walking at $10 \,km / h$. Find his average speed for the whole journey. (in $km/h$)

The average weight of $24$ students is $35\, kgs.$ If the weight of teacher is added the average increased by $400\, gms$. What is the weight of the teacher? (in $kg$)

The average of $6$ observations is $12 .$ A new seventh observation is included and the new average is decreased by $1$. The seventh observation is