A cube is divided into 64 identical cubelets. Each cut is made parallel to some surface of the cube. But before doing that, the cube is painted with green on one set of opposite faces, red on another set of opposite faces, and blue on the third set of opposite faces. How many cubelets are painted with exactly one colour?
Select:  A) 12  B) 16  C) 20  D) 24  E) 30
Each side of the cube has 4 x 4 = 16 cubelets.   Only the interior cubelets are painted one colour.   On each side, 2 x 2 = 4 cubelets are painted one colour.   Since the cube has six sides, the number of cubes with one colour is  6*4= 
<gadget id="calculator"> 6*4</gadget>
<output>24</output>
24   The answer is 24.
<result>D</result>
A cube is divided into 64 identical cubelets. Each cut is made parallel to some surface of the cube. But before doing that, the cube is painted with green on one set of opposite faces, red on another set of opposite faces, and blue on the third set of opposite faces. How many cubelets are painted with exactly one colour?