If the price of petrol is increased by $20 \%$,by what percentage should the consumption be decreased by the consumer,if the expenditure on petrol remains unchanged (in $\%$)?

Which number is $60 \%$ less than $80$?

Aditya's salary was increased by $40 \%$ and then decreased by $25 \%$. Find the net effect on Aditya's salary.

Two-thirds of three-fourths of one-fifth of a number is $15$. What is $30$ per cent of that number?

Five-ninths of a number is equal to $25$ per cent of the second number. The second number is equal to one-fourth of the third number. The value of the third number is $2960$. What is $30$ per cent of the first number?

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.