3.9 is what percent of 80 - 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 80 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 80, so we can write it down as 100%=80.
4. We know, that x% equals 3.9 of the output value, so we can write it down as x%=3.9.
5. Now we have two simple equations:
1) 100%=80
2) x%=3.9
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%=80/3.9
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 3.9 is what percent of 80

100%/x%=80/3.9
(100/x)*x=(80/3.9)*x       - we multiply both sides of the equation by x
100=20.512820512821*x       - we divide both sides of the equation by (20.512820512821) to get x
100/20.512820512821=x
4.875=x
x=4.875

now we have:
3.9 is 4.875% of 80