Given weight in kg is: 54,59,x,53,73,49,50,58,45.
We know, Mean is given by,
Mean=Sum of the elementsTotal number of elements.
Here, the number of members =9.
Also, average weight =56kg.
⟹ 56=54+59+x+53+73+49+50+58+459
⟹ 56=441+x9
⟹ 56×9=441+x
⟹ 504=441+x
⟹ x=504−441=63kg.
Therefore, option D is correct.