The average age of $8$ members of a group is $40 \,years.$ The age of $1$ member is $55\, years.$ After his retirement a new member comes in his place of age $39 .$ What is the effect of his retirement on the average age of group ?
$2$
$0$
$3$
$5$
The average of marks obtained by $150$ candidates in a certain examination is $50 .$ If the average marks of passed candidates is $55$ and that of the failed candidates is $25,$ what is the number of candidates who passed the examination?
Out of nine persons, eight persons spent $Rs. \,30$ each for their meals. The ninth one spent $Rs. \,20$ more than the average expenditure of all the nine. The total money spent by all of them was (in $Rs.$)
The average of nine numbers is $50.$ The average of the first five numbers is $54$ and that of the last three numbers is $52 .$ Then the sixth number is?
The average age of a cricket team reduces by $2$ when two senior players aged $32$ and $30$ are replaced by $2$ youngsters of equal age. What is the age of these players?
A man travels by a car to his office at $60 \,km / h$ and returns home along the same route at $20 \,km / h .$ Find the average speed of his whole journey. (in $km/h$)