399.9 is what percent of 500 - 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 500 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 500, so we can write it down as 100%=500.
4. We know, that x% equals 399.9 of the output value, so we can write it down as x%=399.9.
5. Now we have two simple equations:
1) 100%=500
2) x%=399.9
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%=500/399.9
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 399.9 is what percent of 500

100%/x%=500/399.9
(100/x)*x=(500/399.9)*x       - we multiply both sides of the equation by x
100=1.2503125781445*x       - we divide both sides of the equation by (1.2503125781445) to get x
100/1.2503125781445=x
79.98=x
x=79.98

now we have:
399.9 is 79.98% of 500