$A$ pair of articles was bought for $Rs. 37.40$ at a discount of $15 \%$. What must be the marked price of each of the articles?

$A$ man sold his two horses for $Rs. 770$ each. On one he gained $10\%$ and on the other he lost $10\%$. The average gain or loss percentage is:

Albert buys $4$ horses and $9$ cows for $Rs. 13400$. If he sells the horses at $10 \%$ profit and the cows at $20 \%$ profit,then he earns a total profit of $Rs. 1880$. The cost price of a horse is (in $Rs.$)

Raman sells a machine for $Rs. 39$ lakh at a loss. Had he sold it for $Rs. 49$ lakh,his gain would have been three times the loss. What is the cost price of the machine? (in $Rs. \text{ lakh}$)

$A$ shopkeeper sold chairs at $Rs. 2139$ each after giving a $7 \%$ discount on the labelled price. Had he not given the discount, he would have earned a profit of $15 \%$ on the cost price. What was the cost price of each chair? (in $Rs.$)

By selling $80$ ball pens for $₹ 140$,a retailer loses $30 \%$. How many ball pens should he sell for $₹ 104$ so as to make a profit of $30 \% ?$