87 is what percent of 640 - 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 640 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 640, so we can write it down as 100%=640.
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%=640
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%=640/87
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 640

100%/x%=640/87
(100/x)*x=(640/87)*x       - we multiply both sides of the equation by x
100=7.3563218390805*x       - we divide both sides of the equation by (7.3563218390805) to get x
100/7.3563218390805=x
13.59375=x
x=13.59375

now we have:
87 is 13.59375% of 640