What is 78 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 640 is 100%, so we can write it down as 640=100%.
4. We know, that x is 78% of the output value, so we can write it down as x=78%.
5. Now we have two simple equations:
1) 640=100%
2) x=78%
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:
640/x=100%/78%
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 78% of 640

640/x=100/78
(640/x)*x=(100/78)*x       - we multiply both sides of the equation by x
640=1.2820512820513*x       - we divide both sides of the equation by (1.2820512820513) to get x
640/1.2820512820513=x
499.2=x
x=499.2

now we have:
78% of 640=499.2