12.9 is what percent of 40 - 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 40 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 40, so we can write it down as 100%=40.
4. We know, that x% equals 12.9 of the output value, so we can write it down as x%=12.9.
5. Now we have two simple equations:
1) 100%=40
2) x%=12.9
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%=40/12.9
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 12.9 is what percent of 40

100%/x%=40/12.9
(100/x)*x=(40/12.9)*x       - we multiply both sides of the equation by x
100=3.1007751937984*x       - we divide both sides of the equation by (3.1007751937984) to get x
100/3.1007751937984=x
32.25=x
x=32.25

now we have:
12.9 is 32.25% of 40