It takes three-thirds to make a whole unit. As a fraction, three-thirds is written as 3/3, which literally means three divided by three, which is then simplified as one. A fraction is a part of a whole, and a whole is equivalent to the figure one.
Any number over itself is equal to one. Using this fact, two-halves are a whole, four-fourths are a whole, ten-tenths are a whole and the list continues. From a practical standpoint, it takes three 1/3 cups to make 1 cup, three 1/3 tablespoons to make 1 tablespoon and three 1/3 inches to make 1 inch.