81.6 is what percent of 20.4 - 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 20.4 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 20.4, so we can write it down as 100%=20.4.
4. We know, that x% equals 81.6 of the output value, so we can write it down as x%=81.6.
5. Now we have two simple equations:
1) 100%=20.4
2) x%=81.6
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%=20.4/81.6
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 81.6 is what percent of 20.4

100%/x%=20.4/81.6
(100/x)*x=(20.4/81.6)*x       - we multiply both sides of the equation by x
100=0.25*x       - we divide both sides of the equation by (0.25) to get x
100/0.25=x
400=x
x=400

now we have:
81.6 is 400% of 20.4