36/51 as a percentage is 70.59%. This is the rounded value you get when you express the fraction in terms of hundredths.
The fraction 36/51 can also be reduced to 12/17, which shows the same relationship between the numbers. Whether you write it as 12/17 or 36/51, the size of the part compared to the whole stays the same.
Knowing that 36 out of 51 is about 70.59% helps when you compare it to other percentages, like test scores or discounts. It’s a quick way to see that the fraction is a little more than two‑thirds of the whole.