$A$ mixture contains $80 \%$ acid and the rest water. What part of the mixture should be removed and replaced by the same amount of water to make the ratio of acid to water $4:3$?

Some amount out of ₹$7000$ was lent at $6 \%$ $p.a.$ and the remaining at $4 \%$ $p.a.$ If the total simple interest from both the fractions in $5$ $years$ was ₹$1600$,the sum lent at $6 \%$ $p.a.$ was (in ₹).

$600 \, gm$ of sugar solution contains $40 \%$ sugar. How much sugar should be added to make the concentration $50 \%$ in the solution? (in $gm$)

In $50\, g$ alloy of gold and silver,the gold is $80\%$ by weight. How much gold should be mixed to this alloy,so that the weight of gold would become $95\%$? (in $g$)

Two alloys contain tin and iron in the ratio of $1:2$ and $2:3$. If the two alloys are mixed in the proportion of $3:4$ respectively (by weight),the ratio of tin and iron in the newly formed alloy is:

$A$ and $B$ are two alloys of gold and copper prepared by mixing metals in the ratio $5:3$ and $5:11,$ respectively. Equal quantities of these alloys are melted to form a third alloy $C.$ The ratio of gold and copper in the alloy $C$ is