What is 640 percent of 20 - 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 20 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 20 is 100%, so we can write it down as 20=100%.
4. We know, that x is 640% of the output value, so we can write it down as x=640%.
5. Now we have two simple equations:
1) 20=100%
2) x=640%
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:
20/x=100%/640%
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for what is 640% of 20

20/x=100/640
(20/x)*x=(100/640)*x       - we multiply both sides of the equation by x
20=0.15625*x       - we divide both sides of the equation by (0.15625) to get x
20/0.15625=x
128=x
x=128

now we have:
640% of 20=128