What is 89.9 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 90 is 100%, so we can write it down as 90=100%.
4. We know, that x is 89.9% of the output value, so we can write it down as x=89.9%.
5. Now we have two simple equations:
1) 90=100%
2) x=89.9%
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:
90/x=100%/89.9%
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for what is 89.9% of 90

90/x=100/89.9
(90/x)*x=(100/89.9)*x       - we multiply both sides of the equation by x
90=1.1123470522803*x       - we divide both sides of the equation by (1.1123470522803) to get x
90/1.1123470522803=x
80.91=x
x=80.91

now we have:
89.9% of 90=80.91