What is 21 percent of 644 - 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 644 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 644 is 100%, so we can write it down as 644=100%.
4. We know, that x is 21% of the output value, so we can write it down as x=21%.
5. Now we have two simple equations:
1) 644=100%
2) x=21%
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:
644/x=100%/21%
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 21% of 644

644/x=100/21
(644/x)*x=(100/21)*x       - we multiply both sides of the equation by x
644=4.7619047619048*x       - we divide both sides of the equation by (4.7619047619048) to get x
644/4.7619047619048=x
135.24=x
x=135.24

now we have:
21% of 644=135.24