A man gains $15 \%$ by selling a calculator for a certain price. If he sells it at the triple the price, then what will be the profit percentage?

A trader purchase 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 profit of $Rs$. $51.50 .$ The difference between the original prices of the pendulum and the watch is equal to? (in $Rs.$)

A shopkeeper professes to sell his goods at cost price but uses a $930$ $gm$ weight instead of $1$ kilogram weight. What will be the profit per cent of the shopkeeper?

Arun purchased $30\, kg$ of wheat at the rate of $Rs.\,11.50$ per $kg$ and $20\, kg$ of wheat at the rate of $Rs.\,14.25$ per $kg$. He mixed the two and sold the mixture. Approximately at what price per $kg$ should he sell the mixture to make $30 \%$ profit? (in $Rs.$)

A sells a suitcase to $B$ at $10 \%$ profit. $B$ cells it to $C$ at $30 \%$ profit. If $C$ pays $Rs.\, 2,860$ for it, then the price at which A bought it is (in $Rs.$)

A man buys $10$ articles for $Rs.\, 8$ and sells them at $Rs.\, 1.25$ per article. His gain percent is