17.91 is what percent of 19.9 - 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 19.9 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 19.9, so we can write it down as 100%=19.9.
4. We know, that x% equals 17.91 of the output value, so we can write it down as x%=17.91.
5. Now we have two simple equations:
1) 100%=19.9
2) x%=17.91
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%=19.9/17.91
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 17.91 is what percent of 19.9

100%/x%=19.9/17.91
(100/x)*x=(19.9/17.91)*x       - we multiply both sides of the equation by x
100=1.1111111111111*x       - we divide both sides of the equation by (1.1111111111111) to get x
100/1.1111111111111=x
90=x
x=90

now we have:
17.91 is 90% of 19.9