If the cost price of $20$ articles is equal to the selling price of $15$ articles,find the profit percent?

$A$ fair price shopkeeper takes $10 \%$ profit on his goods. He lost $20 \%$ of his goods due to theft. What is his loss percentage (in $\%$)?

If the $CP$ of $50$ items is equal to the $SP$ of $40$ items,then what is the profit or loss $\%$ (in $\%$)?

Nutan bought a watch with $24 \%$ discount. If she pays $Rs. 779$ for that watch,then what is the marked price of the watch in $Rs.$?

If a radio is purchased for $Rs. 490$ and sold for $Rs. 465.50$,find the $\text{loss} \%$. (in $\%$)

Arun buys one kilogram of apples for $Rs. 120$ and sells it to Swati gaining $25\%$. Swati sells it to Divya who again sells it for $Rs. 198$,making a profit of $10\%$. What is the profit percentage made by Swati (in $\%$)?