84 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 84 of the output value, so we can write it down as x%=84.
5. Now we have two simple equations:
1) 100%=640
2) x%=84
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%=640/84
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 84 is what percent of 640

100%/x%=640/84
(100/x)*x=(640/84)*x       - we multiply both sides of the equation by x
100=7.6190476190476*x       - we divide both sides of the equation by (7.6190476190476) to get x
100/7.6190476190476=x
13.125=x
x=13.125

now we have:
84 is 13.125% of 640