By selling an article for Rs. 880, a shopkeeper gains 10%. Due to a reduction in sales, he allows a discount of 25% on the previous selling price. What is his gain or loss percentage during the sale?

A company considers hiring an extra machine for $150 per day to produce additional units. If the additional throughput contribution generated from producing these units on the machine is $390, by how much will total profit increase?

If the cost price of an article is 85 times its selling price, what is the loss percentage?