87 is what percent of 128.9 - 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 128.9 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 128.9, so we can write it down as 100%=128.9.
4. We know, that x% equals 87 of the output value, so we can write it down as x%=87.
5. Now we have two simple equations:
1) 100%=128.9
2) x%=87
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%=128.9/87
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 87 is what percent of 128.9

100%/x%=128.9/87
(100/x)*x=(128.9/87)*x       - we multiply both sides of the equation by x
100=1.4816091954023*x       - we divide both sides of the equation by (1.4816091954023) to get x
100/1.4816091954023=x
67.494181536074=x
x=67.494181536074

now we have:
87 is 67.494181536074% of 128.9