A cuboidal, block of 6 cm X 9 cm X 12 cm is cut up into an exact number of equal cubes. The least possible number of cubes will be_________?

A. 6
B. 9
C. 24
D. 30
Volume of block = (6 X 9 X 12) cm3 = 648 cm3.
Side of largest cube = H.C.F. of 6 cm, 9 cm, 12 cm = 3 cm.
Volume of this cube = (3 X 3 X 3) = 27 cm3.
Number of cubes = 648/27 = 24.