Of the three numbers, the first is twice the second and the second is twice the third. The average of the reciprocal of the numbers is $\frac{7}{72} .$ The numbers are
$16,\,8,\,4$
$20,\,10,\,5$
$24,\,12,\,6$
$36,\,18,\,9$
$16$ children are to be divided into two groups $A$ and $B$ of $10$ and $6$ children. The average percent marks obtained by the children of group $A$ is $75$ and the average per cent marks of all the $16$ children is $76 .$ What is the average per cent marks of children of group $B$ ?
The average of two numbers $A$ and $B$ is $20 ,$ that of $B$ and $C$ is $19$ and of $C$ and $A$ it is $21 .$ What is the value of $A ?$
It rained as much on Wednesday as on all the others days of the week combined. If the average rainfall for the whole week was $3 \,cm $ then how much did it rain on Wednesday? (in $cm$)
The average weight of $15$ oarsmen in a boat is increased by $1.6\, kg$ when one of the crew, who weighs $42\, kg$ is replaced by a new man. Find the weight of the new man (in $kg$)
What is the average of first $10$ even numbers ?