$A$ man spends $15 \%$ of his income. If his expenditure is $Rs$ $75,$ his income (in rupees) is:

The percentage increase in the surface area of a cube when each side is doubled is:

$A$ person scores $45 \%$ of the total marks in the exam and still fails by $40$ marks. The passing percentage of the exam is $55 \%$. What is the maximum marks of the exam?

In $2009$,the food production was $5.5$ million tonnes and in $2010$,the production was $4.4$ million tonnes. Find out the percentage decrease in food production in these two years?

$40 \%$ are the passing marks. $A$ student gets $250$ marks yet fails by $38$ marks. What is the maximum marks?

An empty fuel tank of a car was filled with an ordinary type of petrol. When the tank was one-third empty,it was filled with high-speed petrol. Again,when the tank was one-third empty,it was filled with an ordinary type of petrol. Again,when the tank was one-third empty,it was filled with high-speed petrol. At this time,what was the percentage of high-speed petrol in the tank?