A person purchases $8$ pens for ₹ $10$ and sells $10$ pens for ₹ $8.$ How much profit or loss does he make in ?

A man loses $20 \frac{1}{2} \%$ of his money and after spending $80 \%$ of the remainder, he is left with $Rs.\, 159 .$ How much did he have at first? (in $Rs.$)

Half of $100$ articles were sold at a profit of $20 \%$ and the rest at a profit of $40 \% .$ If all of the articles had been sold at a profit of $25 \%,$ the total profit would have been $Rs.\,100$ less than earlier profit. The cost price of each article was (in $Rs.$)

A man buys two chairs for a total cost of $900.$ By selling one for $\frac{4}{5}$ of its cost and the other for $\frac{5}{4}$ of its cost, he makes a profit of $90$ on the whole transaction. The cost of the lower priced chair is (in $Rs.$)

If a company sells a car with a marked price of $Rs$ $272000$ and gives a discount of $4 \%$ on $Rs$ $200000$ and $2.5\%$ on the remaining amount of $Rs$ $72000,$ then the actual price charged by the company for the car is (in $Rs.$)

Mr Verma sold his scooter for $Rs.\,10500$ at a gain of $5 \%$. Find out the cost price of the scooter. (in $Rs.$)