Introduction to Fractions. Pizza. Let me order another pizza. Large Pizza. I will divide the pizza into equal parts. This pizza is a whole. 1, 2, 3, 4, 5, 6. Divide the pizza into 6 equal parts. One out of these, six parts can be expressed as one upon six. This number is read as one sixth. Two out of six parts can be expressed as two upon six and read as two sixth. Such type of numbers are called fractions. Whole. Part. Fractions express a part of a whole. 1 upon 6. Fractions can be written using two whole numbers and a line. Number above the line is called numerator. Number below the line is called denominator. Whole. Parts. Denominator tells us total number of parts in a whole. Numerator tells us how many parts are taken from the whole. Whole. Note that, denominator cannot be zero because we cannot make zero parts of a whole. The End.