The ratio of the number of boys and girls in a school is $8: 12$. If $50 \%$ of boys and $25 \%$ of girls are getting scholarships for their studies,what is the percentage of school students who are not getting any scholarships (in $\%$)?

Two alloys contain zinc and copper in the ratio of $2:1$ and $4:1$. In what ratio should the two alloys be mixed to get a new alloy having zinc and copper in the ratio of $3:1$?

If $6 A = 11 B = 7 C$,find $A : B : C$.

$A$ mixture contains alcohol and water in the ratio of $12: 5$. On adding $14 \text{ litres}$ of water,the ratio of alcohol to water becomes $4: 3$. The quantity of alcohol in the mixture is (in $\text{litres}$):

Arti has coins of the denomination of $Rs. 1$,$50 \text{ paise}$,and $25 \text{ paise}$ in the ratio of $12: 10: 7$. The total worth of the coins she has is $Rs. 75$. Find the number of $25 \text{ paise}$ coins.

In an army selection process,the ratio of selected to unselected candidates was $5:1$. If $100$ fewer candidates had applied and $20$ fewer had been selected,the ratio of selected to unselected candidates would have been $6:1$. How many candidates had applied for the process?