The sum of three numbers is $98 .$ If the ratio between the first and second is $2: 3$ and that between the second and the third is $5: 8$ , then the second number is

The average age of $20$ boys in the class is $15.6\, years.$ Five new boys join and the new average becomes $15.56\, years.$ What is the average age of the five new boys? (in $years$)

The average weight of $A, B$ and $C$ is $84 \,kgs.$ If $D$ joins, the average weight now is $80 \,kgs$. If another person $E$ who is $3\, kgs$ heavier than $D$ replaces $A$ then the average weight of $B, C, D$ and $E$ becomes $79\, kgs.$ what is the weight of $A $ in $kg$ ?

The cost of $5 \,kg$ of apples is $Rs.\, 450 .$ The cost of $12$ dozen mangoes is $Rs.\, 4320$, and the cost of $4 \,kg$ of oranges is $Rs.\,240.$ What is the total cost of $8 \,kg$ of apples$, 8$ dozens of mangoes and $8 \,kg$ of oranges ? (in $Rs.$)

Out of four numbers the average of the first three is $16$ and that of the last three is $15 .$ If the last number is $20$ then the first number is

If the average of $m$ numbers is $n^{2}$ and that of $n$ numbers is $m^{2},$ then the average of $( m + n )$ numbers is