What is 0.25 percent of 21 - 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 21 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 21 is 100%, so we can write it down as 21=100%.
4. We know, that x is 0.25% of the output value, so we can write it down as x=0.25%.
5. Now we have two simple equations:
1) 21=100%
2) x=0.25%
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:
21/x=100%/0.25%
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 0.25% of 21

21/x=100/0.25
(21/x)*x=(100/0.25)*x       - we multiply both sides of the equation by x
21=400*x       - we divide both sides of the equation by (400) to get x
21/400=x
0.0525=x
x=0.0525

now we have:
0.25% of 21=0.0525