15 is what percent of 21.57 - 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 21.57 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 21.57, so we can write it down as 100%=21.57.
4. We know, that x% equals 15 of the output value, so we can write it down as x%=15.
5. Now we have two simple equations:
1) 100%=21.57
2) x%=15
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%=21.57/15
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 15 is what percent of 21.57

100%/x%=21.57/15
(100/x)*x=(21.57/15)*x       - we multiply both sides of the equation by x
100=1.438*x       - we divide both sides of the equation by (1.438) to get x
100/1.438=x
69.541029207232=x
x=69.541029207232

now we have:
15 is 69.541029207232% of 21.57