To calculate a percentage, multiply the two numbers together and divide the result by 100, using the following formula: A x B / 100. For example, if we want to know how much is 30% of 150, just multiply 30 x 150 and then divide the result by 100. Then, we will have 4500 (return of 30 x 150) / 100 = 45. The concept is simple: take 30 units of a number divided into 100 parts; practically, we consider 1 hundredth of 150 which is equivalent to 1.5 and we calculate the desired percentage (in this case, 30) making a multiplication. Thus we will have 1.5 x 30 = 45. The same result is get using the proportion "A: C = B: 100", where A represents the unknown number that we want to know, C is the total and B is the number that quantifies the percentage (100). The relationship between the two numbers will be A: 150 = 30: 100. Since in the proportions the product of the means (30 and 150) is equal to the product of the extremes (A and 100), to know the unknown number A we will have to multiply 30 x 150 and divide the result by 100, obtaining 4500 : 100 = 45. Another explanation of the concept consists in transforming the percentage into a fraction (30% = 30/100, where 30 is the numerator and 100 is the denominator) to multiply by the number which represents the total (0.3 x 150).

In this page, the first calculator (the most used) has been joined by another 9, each of which shows the formula used and the explanation of the result, using the **Direct Calculation** and the Calculation of **Inverse Percentage**.

**Attention: for decimals use the dot and not the comma (,).**

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