By selling an article for $Rs. 21$,a man incurs a loss such that the percentage loss is equal to the cost price. The cost price of the article is (in $Rs.$):

$X$ sells two articles for $Rs. 4,000$ each with no loss and no gain in the transaction. If one was sold at a gain of $25\%$, the other is sold at a loss of ........$\%$.

If the selling price is doubled,the profit triples. Find the profit percent.

$A$ and $B$ jointly made a profit of $Rs. 1650$ and they decided to share it such that $\frac{1}{3}$ of $A$'s profit is equal to $\frac{2}{5}$ of $B$'s profit. Then the profit of $B$ is (in $Rs.$)

$A$ man sells two articles,each for $Rs. 640$. He earns $20\%$ profit on the first and $40\%$ profit on the second. Find his overall percent profit.

The profit earned by selling an article for $Rs. 832$ is equal to the loss incurred when the same article is sold for $Rs. 448$. What should be the selling price for making $50\%$ profit? (in $Rs.$)