The first thing to remember: «eighty percent of four hundreds» it's written as «80% of 400». The symbol «%» is often used to make the mathematical expression shorter.
When they talk about 80% of something, they mean that we need to take 80 fragments of the something Whole. One percent means part per one hundred all the time. And we must remember the rule: «The sum of all parts of the whole is 100%». In fact, you have to divide 400 into 100 fragments and take 80 of them. Let's try to figure it out together. You can find out how much 80% of 400 in several ways.
This site below shows some of these methods and an illustration that will help visualize 80% of 400. By the way, people who learn how to calculate 80% of 400 will be able to do the same with other numbers later. Explore that we have presented for you and get a complete understanding of the topic of interest.
As a bonus to the lesson at the end you will know what is not equal to 80% and learn how to solve this problem too.
Memorizing the formula for calculating percents is the easiest way to solve the problem "What is 80% of 400?”. That's why this method is taught in mathematics lessons of schools, because you do not need to know anything about fractional numbers or proportions. Learning the formula will be enough for calculating. The main thing is to correctly determine its components.
The general formula for calculating percentages looks like that:
There are 400 is the Whole, and 80 is the Percent, but the X is the desired result.
So, you can to get an answer to the question «What is eighty percent of four hundreds»:
Now you know that 80% of 400 it is equal to three hundreds twenty!
If you know how to deal with decimal numbers, then you can use another method. You may to convert the percent as a decimal number. It is easy. You can do this by dividing 80 by 100. Just move the decimal point 2 places to the left. So, 80% in decimal form is equal to 0.8
And next just multiply the resulting decimal number with a Whole (with 400):
You get 320 again! So, we can use equivalent forms of percentages interchangeably and choose the one(s) that best suit our purpose.
It is a good method which can show you what is 80 percent of 400. Recall that 400 is a Whole, and a Whole is 100 Parts.
Let's make an equation from this proportion to calculate the Part. We need to multiply the numbers cross by cross:
Let's solve this equation and find the unknown:
So, 80% of 400 it is 320 again.
Look at the diagram we have drawn for you. It shows 80% of the Whole. The pie chart has 400 fragments, and the blue fragment of the circle is 320, or 80% of 400.
Interestingly, the diagram of 80% from any integer will look the same. Because it is always 80 parts of 100 something. Although the answer to the problem will be different, the picture will be the same. For example, 80% of 100 would be 80, which is 80 parts of 100 parts. And the blue part will always take up 80 percent of the circle, because it's always 80 parts of 100.
Since you know the sum is 100%, so to calculate «What is not equal to 80%» you can subtract 80% from 100%. The next step is to take that percents from 400 (we used the formula again):
Or just subtract 320 from 400:
The lesson is over. We hope that we have shown everything clearly enough for you to become a real expert.