0.42 is what percent of 2.1 - 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 2.1 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 2.1, so we can write it down as 100%=2.1.
4. We know, that x% equals 0.42 of the output value, so we can write it down as x%=0.42.
5. Now we have two simple equations:
1) 100%=2.1
2) x%=0.42
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%=2.1/0.42
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 0.42 is what percent of 2.1

100%/x%=2.1/0.42
(100/x)*x=(2.1/0.42)*x       - we multiply both sides of the equation by x
100=5*x       - we divide both sides of the equation by (5) to get x
100/5=x
20=x
x=20

now we have:
0.42 is 20% of 2.1