Three containers whose volumes are in the ratio of $2:3:4$ are full of a mixture of spirit and water. In the $1^{st}$ container,the ratio of spirit to water is $4:1$,in the $2^{nd}$ container the ratio is $11:4$,and in the $3^{rd}$ container the ratio is $7:3$. All three mixtures are mixed in a big container. The ratio of spirit and water in the resultant mixture is:

Pure milk costs $16 / L$. After adding water,the milkman sells the mixture at $15 / L$ and thereby makes a profit of $25 \%$. In what respective ratio does he mix milk with water?

$729 \ ml$ of a mixture contains milk and water in the ratio $7:2$. How much more water is to be added to get a new mixture containing milk and water in the ratio $7:3$? (in $ml$)

$50 \, g$ of an alloy of gold and silver contains $80 \%$ gold (by weight). The quantity of gold,that is to be mixed with this alloy,so that it may contain $95 \%$ gold,is (in $g$)

$18 \text{ litre}$ of pure water was added to a vessel containing $80 \text{ litre}$ of pure milk. $49 \text{ litre}$ of the resultant mixture was then sold,and some more quantity of pure milk and pure water was added to the vessel in the respective ratio of $2:1$. If the resultant respective ratio of milk and water in the vessel was $4:1$,what was the quantity of pure milk added in the vessel? (in $\text{litre}$)

$A$ merchant mixes three varieties of rice costing $Rs. 20$ per $kg$,$Rs. 24$ per $kg$,and $Rs. 30$ per $kg$ and sells the mixture at a profit of $20\%$ at $Rs. 30$ per $kg$. How many $kgs$ of the second variety will be in the mixture if $2$ $kgs$ of the third variety is there in the mixture?