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 $kgs$?

The marked price of a piano was $Rs.\, 15,000$. At the time of sale, there were successive discounts of $20 \%$ $10 \%$ and $10 \%$ on it. The sale price was (in $Rs.$)

A discount series of $10 \%, 20 \%$ and $40 \%$ is equal to a single discount of.......$\%$

A merchant advertises $10 \%$ off on the items bought from his store. The total discount got by a customer who bought a cooker worth $Rs.\,650,$ a heater worth $Rs.\,500$ and a bag worth $Rs.\,65$ is (in $Rs.$)

Profit obtained on selling an article for $Rs.\,310$ is equal to the loss incurred on selling that article for $Rs.\, 230.$ What will be the loss percentage when selling price is $Rs.\, 180$?

The marked price of a watch was $Rs.\,720.$ A man bought the same for $Rs.\, 550.80$ after getting two successive discounts, the first being $10 \% .$ The second discount rate is.......$\%$