On selling a calculator for Rs. 980, a person loses 623%. For how much (in Rs.) should he sell it to gain 8%?

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?