1 kilogram= 3-4 pieces (approx.)
Orange is a hybrid between pomelo and mandarin, there are 600 types of them which are classified into three: sweet, bitter/sour and loose-skinned.
Navel Oranges belong to the sweet orange varieties. The name "navel orange" comes from the belly-button formation opposite the fruit's stem end. The bigger the navel, the sweeter the orange.