24 cubes 1x1x1
Just one, although the orientation of the prism might vary.
-- Start out with 40 identical cubes. -- Take 8 of them. Place them on the table in 2 rows, 4 cubes in each row, without any spaces between them. -- Take four more groups of 8 cubes. On other places on the table, arrange each group in 2 rows of 4 in each row, just like you did the first group. -- Pile all five groups up on top of each other, neatly, in one pile of five layers. Pile them carefully, so that all the sides of the pile are flat, straight, and smooth. There should be no holes in the pile, and you should have no cubes left over. The pile of five layers is the rectangular prism you want.
The answer depends on their relative dimensions.
Without cutting the cubes and using all of them 2 different oblongs can be made: 1 by 6 and 2 by 3.
A rectangular prism that is 4 cubes by 2 cubes is made up of 8 cubes.
A rectangular prism.
by placing 5 cubes in one row and another in above row.
8.33
48/6 = 8 cm
24 cubes 1x1x1
120
Just one, although the orientation of the prism might vary.
100 cubic cm
A larger rectangular prism.
48 unit cubes
-- Start out with 40 identical cubes. -- Take 8 of them. Place them on the table in 2 rows, 4 cubes in each row, without any spaces between them. -- Take four more groups of 8 cubes. On other places on the table, arrange each group in 2 rows of 4 in each row, just like you did the first group. -- Pile all five groups up on top of each other, neatly, in one pile of five layers. Pile them carefully, so that all the sides of the pile are flat, straight, and smooth. There should be no holes in the pile, and you should have no cubes left over. The pile of five layers is the rectangular prism you want.