6/40 as a percentage is 15.00%. This is the rounded value you get when you express the fraction in terms of hundredths.
The fraction 6/40 can be simplified to 3/20, which is an easy way to see how small the part is compared to a whole. Even without the math details, you can think of it as 15 out of every 100 parts.
In everyday language, saying something is 15.00% means it takes up fifteen percent of the total. That’s a handy number to remember when you compare parts of a whole in reports, projects, or simple calculations.