If the true discount on $Rs. 161$ due for $2$ years and $6$ months is $Rs. 21$, then find the rate of interest (in $\%$).

$A$ $Rs. 750$ tin of cheese is offered at $8\%$ discount and a $Rs. 1,250$ tin of butter at $20\%$ discount. If we buy $5$ tins of cheese and $3$ tins of butter,what is the effective discount we get (in $\%$)?

If $21 \%$ of an electricity bill is discounted,$Rs. 1817$ is still to be paid. How much was the original bill amount? (in $Rs.$)

While selling a shirt,a shopkeeper gives a discount of $7 \%$. If he gives a discount of $9 \%$,he earns $Rs. 15$ less in profit. The marked price of the shirt is (in $Rs.$):

If the simple interest on $Rs. 2000$ at $5\%$ $p.a.$ is equal to the true discount on $Rs. 2500$ for the same time and at the same rate,the time is (in $years$)

The present worth of a sum of money due for $146 \text{ days}$ at $5 \%$ is $Rs. 400$. The sum due is (in $Rs.$)