So, volume of cube having edge of length 5cm and all faces are painted =53=125cm3 Let cube be divided into ' n ' small cubes of unit volume. Volume of big cube =n× volume of unit volume cube 125=n×1⇒n=125 Now, Number of cubes whose 3 faces are painted =8 Number of cubes whose 2 faces are painted =36 Number of cubes whose l face is painted =54 Number of cubes whose 0 face is painted =125−(8+36+54)=27 ∵ Required probability