81.15 is what percent of 90 - 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 90 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 90, so we can write it down as 100%=90.
4. We know, that x% equals 81.15 of the output value, so we can write it down as x%=81.15.
5. Now we have two simple equations:
1) 100%=90
2) x%=81.15
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%=90/81.15
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 81.15 is what percent of 90

100%/x%=90/81.15
(100/x)*x=(90/81.15)*x       - we multiply both sides of the equation by x
100=1.1090573012939*x       - we divide both sides of the equation by (1.1090573012939) to get x
100/1.1090573012939=x
90.166666666667=x
x=90.166666666667

now we have:
81.15 is 90.166666666667% of 90