$20 \%$ loss on selling price is what per cent loss on the cost price? (in $\%$)

An article is sold at a profit of $20 \%$. If both the cost price and selling price are $Rs. 150$ less,the profit would be $5 \%$ more. Find the cost price.

$A$ man sells an article at $5 \%$ above its cost price. If he had bought it at $5 \%$ less than what he had paid for it and sold it at $Rs. 2$ less,he would have gained $10 \%$. The cost price of the article is (in $Rs.$)

$60 \%$ of the cost price of an article is equal to $50 \%$ of its selling price. Then the percentage of profit or loss on the cost price is

$A$ trader purchases a wrist watch and a pendulum for $Rs. 390$. He sells them making a profit of $10 \%$ on the watch and $15 \%$ on the pendulum. He earns a total profit of $Rs. 51.50$. The difference between the original prices of the pendulum and the watch is equal to? (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 $Rs.$)