What is Profit Percentage

I purchase 100 kg of tea and sell it for a profit to the extent of what I would have paid for 40 kg. What is my profit percentage?

If profit is 1/ 9^(th) of selling price, then what is the profit percentage?

Selling price of an article is (8)/(7) of cost price. What is the profit percentage ?

On selling 30 caps, a shopkeeper earns profit equal to the selling price of 3 caps. What is the profit percentage?

The profit on selling 35 mangoes is equal to the cost price of 7 mangoes. What is the profit percentage?