WBCS Mains 2019 Official Paper-VI

A man saves $20\%$ of his income. If his expenses are increased by $35\%$, by what percent must his income be raised so that he can save $10\%$ of his new income?

A mixture of milk and water contains $12\frac{1}{2}$ of water. How much water should be added to $200\text{gallons}$ of such a mixture so that the new mixture may contain $37\frac{1}{2}$ of water?

One litre of spirit which contains $10\%$ of water is added to $3\text{litres}$ of spirit containing $7\%$ of water, and to this mixture half a litre of water is added. Find the percentage of water in the final mixture.

A certain kind of brass is composed of copper, zinc, lead and tin. The ratio of copper to zinc is $1:2$, of zinc to lead is $3:5$ and of lead to tin is $7:8$. Find the quantity of each metal in $213\text{gm}$ of brass.

If $25$ men can weave $120\text{metres}$ of cloth in a day, how many metres of cloth will be woven by $35$ men in a day?