20 is what percent of 128.4 - 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 128.4 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 128.4, so we can write it down as 100%=128.4.
4. We know, that x% equals 20 of the output value, so we can write it down as x%=20.
5. Now we have two simple equations:
1) 100%=128.4
2) x%=20
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%=128.4/20
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 20 is what percent of 128.4

100%/x%=128.4/20
(100/x)*x=(128.4/20)*x       - we multiply both sides of the equation by x
100=6.42*x       - we divide both sides of the equation by (6.42) to get x
100/6.42=x
15.576323987539=x
x=15.576323987539

now we have:
20 is 15.576323987539% of 128.4