78 is what percent of 3900 - 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 3900 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 3900, so we can write it down as 100%=3900.
4. We know, that x% equals 78 of the output value, so we can write it down as x%=78.
5. Now we have two simple equations:
1) 100%=3900
2) x%=78
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%=3900/78
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 78 is what percent of 3900

100%/x%=3900/78
(100/x)*x=(3900/78)*x       - we multiply both sides of the equation by x
100=50*x       - we divide both sides of the equation by (50) to get x
100/50=x
2=x
x=2

now we have:
78 is 2% of 3900