An ore contains $23 \%$ copper. To get $69 \text{ kg}$ of copper, the quantity of the ore required is: (in $\text{ kg}$)

$A$ man spends $75 \%$ of his income. His income is increased by $20 \%$ and he increases his expenditure by $10 \%$. By what percentage does his saving increase (in $\%$)?

$A$ salesman is allowed $5 \frac{1}{2} \%$ discount on the total sales made by him plus a bonus of $\frac{1}{2} \%$ on the sales made over $₹ 10000$. If his total earnings are $₹ 1990$,find the total sales.

Sashi has $Rs. 90000$ with him. He purchases a mobile,an iPad,and a laptop for $Rs. 15000$,$Rs. 13000$,and $Rs. 35000$ respectively and puts the remaining money in his bank account which pays $15 \%$ per annum compound interest. After $2$ years,he sells off the three items at $80 \%$ of their original price and also withdraws his entire money from the bank by closing the account. What is the total percentage change in his assets (in $\%$)?

The average salary of male employees in a firm was $Rs$ $5200$ and that of females was $Rs$ $4200$. The mean salary of all the employees was $Rs$ $5000$. What is the percentage of female employees?

If $12 \%$ of $x$ is equal to $6 \%$ of $y,$ then $18 \%$ of $x$ will be equal to how much per cent of $y$ ?