30/70 as a percentage is 42.86%. This is the rounded value you get when you express the fraction in terms of hundredths.
The fraction 30/70 can be simplified to 3/7, which still represents the same part of a whole. Seeing it as a percentage makes it easier to compare with other values that are already in percent form.
In everyday situations, you might use 42.86% to describe things like the portion of a budget, a test score, or a survey result. It tells you that just under half of the total is represented by the 30 out of 70 units.
