. Use the total number of marbles. This is 30.
Divide the number of blue marbles into the total: 12/30 = 0.4. Multiple this value by 100 to get the percent: 0.4 x 100 = 40% are blue. You have two ways to determine what percent are not blue. The easiest is to take the total percent minus the percent that are blue: 100% - 40% = 60% not blue.
How to Calculate Percentages. To calculate the percentage of a specific number, you first convert the percentage number to a decimal. This process is the reverse of what you did earlier. You divide your percentage by 100. So, 40% would be 40 divided by 100 or.40.
![Percentage Percentage](/uploads/1/2/5/3/125379457/343013274.jpg)
You could calculate it, just like you did the initial blue marble problem. You know the total number of marbles.
The number that is not blue is the total minus the blue marbles: 30 - 12 = 18 non-blue marbles.The percent that is not blue is 18/30 x 100 = 60% As a check, you can make sure the total of blue and non-blue marbles adds up to 100%: 40% + 60% = 100%.