What is 10 percent of 39.991 - 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 39.991 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 39.991 is 100%, so we can write it down as 39.991=100%.
4. We know, that x is 10% of the output value, so we can write it down as x=10%.
5. Now we have two simple equations:
1) 39.991=100%
2) x=10%
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:
39.991/x=100%/10%
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 10% of 39.991

39.991/x=100/10
(39.991/x)*x=(100/10)*x       - we multiply both sides of the equation by x
39.991=10*x       - we divide both sides of the equation by (10) to get x
39.991/10=x
3.9991=x
x=3.9991

now we have:
10% of 39.991=3.9991