The salary of a person was reduced by $10 \%$. By what percent should his reduced salary be raised so as to bring it at par with his original salary (in $\%$)?

Two shopkeepers sell a radio of similar brand and type at the same list price of $₹ 1000$. The first allows two successive discounts of $20 \%$ and $10 \%$,and the second allows two successive discounts of $15 \%$ and $15 \%$. Find the difference in discounts offered by the two shopkeepers.

In the laptop market,only three competitors (Lenovo,Apple,and Samsung) exist. Last year,the sales of Apple laptops were $10 \%$ more than Lenovo. This year,both the firms Lenovo and Apple increased their respective sales by $20 \%$. This year,the sales of the firm Apple are five times that of Samsung. What percentage of the total market sales did Samsung account for last year,if the total sales remained constant over the two-year period (in $\%$)?

How many litres of pure acid are there in $8$ litres of a $20\%$ solution?

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

The ratio $5: 4$ expressed as a percentage is: (in $\%$)