20 is what percent of 390 - 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 390 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 390, so we can write it down as 100%=390.
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%=390
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%=390/20
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 390

100%/x%=390/20
(100/x)*x=(390/20)*x       - we multiply both sides of the equation by x
100=19.5*x       - we divide both sides of the equation by (19.5) to get x
100/19.5=x
5.12820512821=x
x=5.12820512821

now we have:
20 is 5.12820512821% of 390