The first thing to remember: «eighty one percent of forty five» it's written as «81% of 45». The symbol «%» is often used to make the mathematical expression shorter.
When they talk about 81% of something, they mean that we need to take 81 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 45 into 100 fragments and take 81 of them. Let's try to figure it out together. You can find out how much 81% of 45 in several ways.
This site below shows some of these methods and an illustration that will help visualize 81% of 45. By the way, people who learn how to calculate 81% of 45 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 81% and learn how to solve this problem too.
Memorizing the formula for calculating percents is the easiest way to solve the problem "What is 81% of 45?”. 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 45 is the Whole, and 81 is the Percent, but the X is the desired result.
So, you can to get an answer to the question «What is eighty one percent of forty five»:
Now you know that 81% of 45 it is equal to thirty six!
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 81 by 100. Just move the decimal point 2 places to the left. So, 81% in decimal form is equal to 0.81
And next just multiply the resulting decimal number with a Whole (with 45):
You get 36.45 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 81 percent of 45. Recall that 45 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, 81% of 45 it is 36.45 again.
Look at the diagram we have drawn for you. It shows 81% of the Whole. The pie chart has 45 fragments, and the blue fragment of the circle is 36.45, or 81% of 45.
Interestingly, the diagram of 81% from any integer will look the same. Because it is always 81 parts of 100 something. Although the answer to the problem will be different, the picture will be the same. For example, 81% of 100 would be 81, which is 81 parts of 100 parts. And the blue part will always take up 81 percent of the circle, because it's always 81 parts of 100.
Since you know the sum is 100%, so to calculate «What is not equal to 81%» you can subtract 81% from 100%. The next step is to take that percents from 45 (we used the formula again):
Or just subtract 36.45 from 45:
The lesson is over. We hope that we have shown everything clearly enough for you to become a real expert.