Find the mean proportional between $9$ and $64$.

Four years ago,the father's age was three times the age of his son. The total of the ages of the father and the son after four years will be $64$ years. What is the father's age at present (in years)?

The ratio of boys and girls in a school is $9:5$. If the total number of students in the school is $1050$,then the number of boys is

Among $132$ examinees of a certain school,the ratio of successful to unsuccessful students is $9:2$. Had $4$ more students passed,then the ratio of successful to unsuccessful students would have been:

$Rs. 2186$ is distributed among $A$,$B$,and $C$. If the money given to them is decreased by $Rs. 26$,$Rs. 28$,and $Rs. 32$ respectively,then the ratio of their shares becomes $9: 13: 8$. What is the amount (in $Rs.$) given to $A$?

If an alloy contains copper and silver in the ratio $3:7$,then the percentage quantity of silver in the alloy is