Answer : The density of book is

The mass of a ball is, 50 grams.
Explanation :
Part 1 :
Density : It is defined as the mass contained per unit volume.
Formula used :

Given :
Mass = 1800 g
Volume =

Now put all the given values in the above formula, we get :

Therefore, the density of book is

Part 2 :
Formula used :

Given :
Volume =

Density =

Now put all the given values in the above formula, we get :


Therefore, the mass of a ball is 50 grams.