Take the new price (5.00) and deduct the old price ( 4.00) from it. Then divide the result by the old price and then multiply by 100 for percent.

5.00 minus 4.00 = 1.00, 1.00 div. By 4.00 = 0.25 times 100 = 25%

5.00 minus 4.00 = 1.00, 1.00 div. By 4.00 = 0.25 times 100 = 25%