How many chromosomes will be present in a diploid cell at mitotic anaphase, if its egg cell has ten chromosomes?

Mitosis is known as equational division as the ploidy level of the cell i.e. number of chromosomes remain same after division. 

At anaphase, chromosomes are pulled apart towards opposite poles of the cell which later divide to form two daughter cells. Thus, two daughter cells are bound by a ingle cell membrane at anaphase and each of these cells will have same number of chromosomes as that of parent cell. As the egg cell has 10 chromosomes, and the daughter cells formed will also have same number of chromosomes when the egg cell undergo mitotic division, therefore, number of chromosomes present in the diploid cell at mitotic anaphase will be 10 + 10 = 20.