The mean weight of $34$ students of a school is $42\, kg$. If the weight of the teacher is included, the mean weight increases by $400\, g$. Find the weight (in $kg$) of the teacher.

Visitors to a show were charged $Rs. 15$ each on the first day,$Rs. 7.50$ on the second day,$Rs. 2.50$ on the third day,and the total attendance on the three days was in the ratio $2:5:13$ respectively. The average charge per person for the entire three days is (in $Rs.$):

The average salary,per head,of all the workers of an institution is $Rs.\, 60$. The average salary of $12$ officers is $Rs.\, 400$; the average salary,per head,of the rest is $Rs.\, 56$. The total number of workers in the institution is:

$A$ cricketer whose bowling average is $12.4$ runs per wicket takes $5$ wickets for $26$ runs and thereby decreases his average by $0.4$. The number of wickets taken by him till the last match was:

The average weight of five persons sitting in a boat is $38\, kg$. The average weight of the boat and the persons sitting in the boat is $52\, kg$. What is the weight of the boat (in $kg$)?

The average age of $A, B, C, D$ five years ago was $45$ years. By including $x$,the present average age of all the five is $49$ years. The present age of $x$ is (in years):