<p>A large solid cube is assembled by gluing together identical unpainted small cubic blocks. All six faces of the large cube are then painted red. If exactly 27 of the small cubic blocks that make up the large cube have no red paint on them, how many small cubic blocks make up the large cube?</p>
<p>Answer: 5x5x5=125</p>
<p>I know the core of the cube is 3x3x3 but why couldn't the answer be 4x4x4?
Can someone explain why it is 5x5x5?</p>
<p>Thank you!</p>
<p>Because you need a complete frame around the 3x3x3 cube…so a complete row all the way around- this would require 5 cube faces ( one on each side plus the 3 in the middle)</p>
<p>I still don’t understand quite honestly :(</p>
<p>Where is this 5 coming from :(</p>
<p>Why couldn’t you just leave it as 4X4X4? It would also create 5 cube faces.</p>
<p>Think of a frame completely encircling the 3x3 cube…there would be a row of cube faces to the left, a row to the right, one on top and one below…that would be two new cubes plus the original 3… Try drawing it out…</p>