638.5 is what percent of 780 - 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 780 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 780, so we can write it down as 100%=780.
4. We know, that x% equals 638.5 of the output value, so we can write it down as x%=638.5.
5. Now we have two simple equations:
1) 100%=780
2) x%=638.5
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%=780/638.5
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 638.5 is what percent of 780

100%/x%=780/638.5
(100/x)*x=(780/638.5)*x       - we multiply both sides of the equation by x
100=1.221613155834*x       - we divide both sides of the equation by (1.221613155834) to get x
100/1.221613155834=x
81.858974358974=x
x=81.858974358974

now we have:
638.5 is 81.858974358974% of 780