A shopkeeper sells an article at a gain of $10 \% .$ Had he sold it at a loss of $20 \%,$ its selling price would have been $Rs.\,180$ less. What is the cost price of the article? (in $Rs.$)

A shopkeeper allows a discount of $10 \%$ on the marked price of an item but charges a sales tax of $8 \%$ on the discounted price. If the customer pays $Rs.\, 3,402$ as the price including the sales tax, then the marked price is (in $Rs.$)

An article is sold at a gain of $15 \% .$ Had it been sold for $Rs.\,27$ more, the profit would have been $20 \%$. The cost price of the article is (in $Rs.$)

A men sells two houses at the rate of $Rs.\,1.995$ Lakhs each. On one house he gains $20 \%$ and on the other he loses $20 \% .$ His gain or loss per cent in the whole transaction is

Seema sells a pen to Sapna at a profit of $25 \% .$ Sapna sells it to Asha at a profit of $10 \%$ and Asha sells it to Kavita at a profit of $5 \%$. If Asha sells it for $Rs.\,231,$ find the cost price at which Seema bought the pen? (in $Rs.$)