The present worth of a certain sum due sometime hence is $Rs. 1700$ and the true discount is $Rs. 170$. The banker's gain is (in $Rs.$)

The holder of a bill for $Rs. 17850$ nominally due on $May 21, 1991$ received $Rs. 357$ less than the amount of the bill by having it discounted at $5 \%$. When was it discounted?

If after giving a discount of $18 \%$,a book is sold for $Rs. 1599$,what will be the marked price (in $Rs.$) of the book?

$A$ shopkeeper gives two successive discounts of $7 \%$ each on the marked price of $Rs.\, 20,000$ of an article. The selling price of the article is (in $Rs.$):

The $T.D.$ on $Rs. 936$ due after a certain time at $8\%$ per annum is $Rs. 36$. The money is due after (in months):

$1$ packet of biscuits costs $Rs.\, 16$,but a pack of $4$ of the same packets of biscuits costs $Rs.\, 56$. What is the effective discount (in $\%$) on the pack?