What is 40 percent of 19.91 - 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 19.91 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 19.91 is 100%, so we can write it down as 19.91=100%.
4. We know, that x is 40% of the output value, so we can write it down as x=40%.
5. Now we have two simple equations:
1) 19.91=100%
2) x=40%
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:
19.91/x=100%/40%
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 40% of 19.91

19.91/x=100/40
(19.91/x)*x=(100/40)*x       - we multiply both sides of the equation by x
19.91=2.5*x       - we divide both sides of the equation by (2.5) to get x
19.91/2.5=x
7.964=x
x=7.964

now we have:
40% of 19.91=7.964