The quality of being easily shaped or moulded is called Plasticity, So Plasticity is the ability of the material to deform without breaking.

Length of the room = 8m 25cm = 825 cm
Breadth of the room = 6m 75cm = 675 cm
Height of the room = 4m 50cm = 450 cm
Prime factorization of 825, 675 and 450 are as follows:
825 = 3×5×5×11
675 = 3×3×3×5×5
450 = 2×3×3×5×5
Common factors = 3×5×5
H.C.F. = 75
Hence, H.C.F. of 825, 675 and 450 is 75.
Therefore the length of the longest tap is 75 cm which can measure the three dimensions of the room exactly.

Lignite coal, is the lowest grade coal with the least concentration of carbon.