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 invests $Rs.\, 21,000$ in shares of a company. He sells one$-$third of total shares at a profit of $10 \% .$ But the remaining shares he has to sell at $5 \%$ loss. Find his overall profit or loss $\%.$

The marked price of a watch was $Rs.\, 720 .$ A man bought the same for $Rs.\, 550.80$ after getting two successive discounts, the first being $10 \% .$ What was the second discount rate? (in $\%$)

A person bought an article for $Rs\,240.$ For how much should he sell it so as to lose $20 \% ?$

A person sold a radio at a loss of $5 \% .$ Had he sold it for $Rs\, 210$ more, he would have gained $25 \%$. For what value should he sell it in order to gain $35 \% ?$

A fruit-seller buys some oranges and by selling $40 \%$ of them he fealises the cost price of all the oranges. As the oranges being to grow over-ripe, he reduces the price and sells $80 \%$ of the remaining oranges at half the previous rate of profit. The rest of the oranges being rotten are thrown away. The overall percentage of profit is