Simple interest on savings
Percent literally means out of 100. 25% means 25 out of 100 or written another way 25/100.
To calculate a percentage of a number use the formula: number x percentage ÷ 100
e.g. To calculate 10% interest on £500
Interest = £500 x 10 ÷ 100 = £50
Percentage increase or decrease
To calculate a percentage increase or decrease use the formula: percentage change = (new value - old value) ÷ old value x 100
e.g. Consider a firm sees that last year they paid £100000 in wages and this year they paid £110000
percentage change = (£110000 - £100000) ÷ £100000 x 100 = 10% increase
To calculate a percentage decrease use the same formula and the sign of the answer signifies whether it is a percentage increase or decrease.
e.g. Last month Charlie earned £30 for walking his Mother's Corgis. This month he only earned £20.
percentage change = (£20 - £30) ÷ £30 x 100 = 33.3% increase