Percent means “for every 100” and it uses symbol % to write a fraction with a denominator of 100 in mathematics. For example, 20% students failed the exam means for every 100 students, there are 20 students that failed the exam.

To calculate the percentage of a number, you need to multiply the number you want the percentage of by the decimal percentage amount. For example, to work out 20% of 300, firstly you need to understand 20% = 20/100 = 0.2, so 20% of 300 = 0.2 x 300 = 60

To calculate the percentage itself, you need to divide the two numbers. For example, there are 300 students, among which 30 students failed the example, what's the percentage of failure? The answer will be 30/300=0.1= 0.1 x 100%= 10%.

To calculate the percentage of increase or decrease between two numbers, you need to divide the difference by the initial number. For example, there are 30 students that failed in 2011, and 40 students failed in 2012, what's the percentage of increase? The answer will be (40-30)/30=0.33 = 0.33 x 100%=33%

You can do some percentage calculation practice here.