Thus, a fraction with a numerator of 1, improper fraction and mixed fraction are usually introduced by the quantity fractions. A fraction with a numerator of 1 such as 1/4 or 1/5 is called ‘a unit fraction’ in Japanese textbooks. A unit fraction is necessary to develops the ideas to recognize a fraction based on a unit fraction, such as 3/4 is three times of 1/4, or 2/5 is two times of 1/5.