Adeline used unit cubes to build a right rectangular prism with a volume of 90 cubic units the height of the prism is 6 units

The question is incomplete. The complete question is :

Adeline used unit cubes to build a right rectangular prism with a volume of 90 cubic units the height of the prism is 6 units.  What figure could be the bottom layer of the prism?

Solution :

It is given that Adeline builds a right rectangular prism with the help of unit cubes. The length breadth and height of a unit cube is one unit each.

The volume of the right rectangular prism is given as, V = 90 cubic units.

The height of the prism is h = 6 units.

Therefore, the volume of the right rectangular prism is :

Volume = length x width x height

90         = length x width x 6

length x width =  

length x width = 15 square units

Now since the each cube is a unit cube, therefore, the bottom layer of the prism will have 5 unit cubes as length and 3 unit cubes as width.

Therefore, the figure (B) is the correct answer.