List of top Data Interpretation & Logical Reasoning (DILR) Questions on Mensuration asked in BHU PET

A solid cube has been formed with 64 smaller cubes. How many smaller cubes are completely invisible?
All the surfaces of a cube of 15 cm side are painted with red colour and then it is cut into smaller cubes of 3 cm side. Then, how many smaller cubes are there having only one surface painted with red colour?