How many chromatids are there in one duplicated chromosome

There are two chromatids in one duplicated chromosome.

Explanation:

Before any cell undergoes the process of cell division, the chromosomes of the cell duplicate themselves. This results in the formation of two chromatids which are known as the sister chromatids. The chromatids are joined together from the centre at a position called the centromere. The chromatids contain the same kind of DNA in them. Chromatids are often confused with homologous chromosomes. They are not homologous chromosomes, they are the copy of a chromosome.