Nisha bought a number of oranges at $2$ for a rupee and an equal number at $3$ for a rupee. To make a profit of $20 \%$ she should sell a dozen for (in $Rs.$)

A loss of $19 \%$ gets converted into a profit of $17 \%$ when the selling price is increased by $Rs.162.$ The cost price of the article is (in $Rs.$)

Oil equal to $20 \%$ of the weight of ground nut is extracted in a mill. The matter left after extraction is sold as cattle feed at the rate of $Rs.\, 12.5$ per $kg$. The ground nuts are bought at $Rs.$ $20$ per $kg.$ the processing cost is $Rs.\, 5$ per $kg$. At what price $(Rs.$ per $kg$ ) should the oil be sold to earn $20 \%$ profit on total costs (Total cost $=$ cost of groundnuts and processing costs)?

Sonal buys mangoes at the rate of $3 \,kgs$ for $Rs$. $21$ and sells them at $5$ $kgs$ for $Rs.$ $50 .$ To earn a profit of $Rs.\,102,$ he must sell how many mangoes in $kgs$?

While selling a watch, a shopkeeper gives a discount of $15 \% .$ If he gives a discount of $20 \%,$ he earns $Rs.\, 51$ less as profit. What is the original price of the watch? (in $Rs$)

By selling an umbrella for $Rs.\, 300,$ a shopkeeper gains $20 \%$. During a clearance sale, the shopkeeper allows a discount of $10 \%$ on the marked price. His gain per cent during the sale is