$A$ person has a chemical costing $Rs. 25$ per $litre$. In what ratio should water be mixed in the chemical so that by selling the mixture at $Rs. 20$ per $litre$,he may get a profit of $25\%$?

Zinc and copper are in the ratio $5:3$ in $400 \, g$ of an alloy. How much copper (in $g$) should be added to make the ratio $5:4$?

In the first alloy,zinc and copper are in the ratio $1:2.$ In the second alloy,the same elements are in the ratio $2:3.$ If these two alloys are mixed to form a new alloy in which the two elements are in the ratio $5:8,$ the ratio of these two alloys in the new alloy is

How many $kg$ of salt at $42$ $P$ per $kg$ must a man mix with $25 \, kg$ of salt at $24$ $P$ per $kg$,so that he may,on selling the mixture at $40$ $P$ per $kg$,gain $25 \%$ on the outlay?

An alloy is made by mixing metal $A$ costing ₹ $2000/kg$ and metal $B$ costing ₹ $400/kg$ in the ratio $A:B = 3:1$. What is the cost (in ₹) of $8$ kilograms of this alloy?

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 ₹).