In order to find what fraction describes this percentage, you first need to know that no matter what percentage you are working with, if you want to convert it into a fraction, put the 35 as the numerator and 100 as the denominator. If you still don't know what I mean, 35 at the top of the fraction and 100 at the bottom. Like this; 35/100. Then, you can simplify it by finding a common multiple between 35 and 100. For example, 5 can be divided into 35 and 100. 35 divided by 5 is 7 and 100 divided by 5 is 20. Your result is 7/20, which can further no more be simplified because there are no more common multiples between the two numbers.
