Ravi purchases $90$ pens and sells $40$ pens at a gain of $10 \%$ and $50$ pens at a gain of $20 \%$. Had he sold all of them at a uniform profit of $15 \%$,he would have got $Rs. 40$ less. Find the cost price of each pen in $Rs$.

Sarita sells a phone at a profit of $20 \%$. If she had bought it at $20 \%$ less and sold it for $Rs. 180$ less, she would have gained $25 \%$. Find the cost price of the phone in $Rs.$

The difference between a discount of $35 \%$ and two successive discounts of $20 \%$ on a certain bill was $Rs$ $22$. Find the amount of the bill in $Rs$.

$A$ vendor buys bananas at $9$ for $Rs. 8$ and sells at $8$ for $Rs. 9$. What will be the profit or loss (in $\%$)?

$A$ garment company declared $15\%$ discount for wholesale buyers. Mr. Ashish bought garments from the company for $Rs. 25000$ after getting the discount. He fixed the selling price of the garments in such a way that he earned a profit of $8\%$ on the original company price. What is the approximate total selling price? (in $Rs.$)

$A$ trader mixes three varieties of groundnuts costing $Rs. 50$,$Rs. 20$,and $Rs. 30$ per $kg$ in the ratio $2:4:3$ by weight and sells the mixture at $Rs. 33$ per $kg$. What is the percentage of profit he makes?