The electricity bill of a certain establishment is partly fixed and partly varies as the number of units of electricity consumed. When in a certain month $540$ units are consumed,the bill is $Rs. 1800$. In another month $620$ units are consumed and the bill is $Rs. 2040$. In yet another month $500$ units are consumed. The bill (in $Rs.$) for that month would be:

If $A$ and $B$ are in the ratio $4:5$ and the difference of their squares is $81,$ what is the value of $A?$

The ratio of the speeds of Aman,Kamal,and Manan is $4: 5: 6$ respectively. What is the ratio of time taken by Aman,Kamal,and Manan respectively to cover the same distance?

In a mixture of petrol and kerosene,the quantity of petrol is $99 \text{ litres}$. If this same quantity of petrol were present in another mixture of petrol and kerosene where the total volume is $198 \text{ litres}$ less than the actual mixture,the concentration of petrol in the actual mixture would be $13.33 \%$ less than that of the new mixture. What is the concentration (in $\%$) of petrol in the actual mixture?

Find the $4^{th}$ proportional to $4, 16$ and $7$.

$A$ certain amount was to be distributed among $A$,$B$,and $C$ in the ratio $2:3:4$,but was erroneously distributed in the ratio $7:2:5$. As a result of this,$B$ received ₹ $40$ less. What is the actual amount (in ₹)?