Percentage is a way of expressing a number as a fraction of 100. It is denoted by the symbol %.

To calculate the percentage of a number, we need to multiply the number by the percentage value and then divide the result by 100.

For example, to find 20% of 50, we can use the following formula:

20% of 50 = (20/100) x 50 = 10

So, 20% of 50 is 10.

Similarly, to find the percentage increase or decrease between two numbers, we can use the following formula:

Percentage increase/decrease = ((new value - old value) / old value) x 100

For example, if the price of a product increased from $50 to $60, we can find the percentage increase as follows:

Percentage increase = ((60 - 50) / 50) x 100 = 20%

So, the price of the product increased by 20%.