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 speed of a cyclist who covers first, second and third km at $20,16$ and $12\, km / hr$ respectively ( in $km / hr )$ is

The average expenditure of a man for the first five months is $Rs.\, 3600$ and for next seven months it is $Rs.\, 3900 .$ If he saves $Rs.\, 8700$ during the $year,$ his average income per $month$ is (in $Rs.$)

A cricketer, whose bowing average was $12.4$ runs/wicket takes $5$ wickets for $22$ runs in a match, thereby decreases his average by $0.4$ The number of wickets, taken by him before this match was

There were $35$ students in a hostel. If the number of students increases by $7,$ the expenses of the mess increase by $Rs. \,42$ per $day$ while the average expenditure per head decreases by $Rs.\, 1 .$ Find the original expenditure of the mess in $Rs.$

A batsman, in his $12^{th}$ innings, makes a score of $63$ runs and thereby increases his average score by $2.$ The average of his score after $12^{th}$ innings is