If a number is increased by $20 \%$ and then reduced by $20 \%$,what is the net change in the number?

$A$'s salary is $40 \%$ of $B$'s salary,which is $25 \%$ of $C$'s salary. What percentage of $C$'s salary is $A$'s salary?

If the price of apple increases from $Rs$ $80$ per $kg$ to $Rs$ $100$ per $kg$,by what percent should a person decrease the consumption of apple so that his expenditure remains the same (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.

The population of a town is $123,456,789$. It increases by $10\%$ during the first year,$20\%$ during the second year,and $30\%$ during the third year. What is the average percentage increase during the three years?

In an examination,a student must get $36 \%$ marks to pass. $A$ student who gets $190$ marks failed by $35$ marks. The total marks in that examination is