42/72 as a percentage is 58.33%. This number tells you how much of a whole 42 parts out of 72 represent when you look at it in terms of 100.
The fraction 42/72 can also be simplified to 7/12, which still gives the same percentage when you convert it. Whether you write it as a fraction or a decimal, the value stays the same.
Knowing the percentage helps you compare it with other numbers that are already in percent form. It’s a quick way to see that 42 out of 72 is a little more than half of the whole.