When a thing is sold for more than it cost the seller, it is said to be
sold at a profit. If it is sold for less than the cost, it is sold at a
loss. Hence,
Profit = Selling Price - Cost Price.
Loss = Cost Price - Selling Price.
A profit or loss is generally reckoned as a percentage.
It is always understood that the percentage is reckoned on the cost
price.
EXAMPLE: I buy wheat at 60 cents and sell it for 75 cents. What per cent
do I gain?
SOLUTION: I gain the difference between 75 cents and 60 cents, or 15
cents. 15 cents is 25% of the cost. Hence, I gain 25%.