8.1 is what percent of 20 - step by step solution

To get the solution, we are looking for, we need to point out what we know.

1. We assume, that the number 20 is 100% - because it's the output value of the task.
2. We assume, that x is the value we are looking for.
3. If 100% equals 20, so we can write it down as 100%=20.
4. We know, that x% equals 8.1 of the output value, so we can write it down as x%=8.1.
5. Now we have two simple equations:
1) 100%=20
2) x%=8.1
where left sides of both of them have the same units, and both right sides have the same units, so we can do something like that:
100%/x%=20/8.1
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 8.1 is what percent of 20

100%/x%=20/8.1
(100/x)*x=(20/8.1)*x       - we multiply both sides of the equation by x
100=2.46913580247*x       - we divide both sides of the equation by (2.46913580247) to get x
100/2.46913580247=x
40.5=x
x=40.5

now we have:
8.1 is 40.5% of 20