a) 120 = 2^3 × 3 × 5
180 = 2^2 × 3^2 × 5
240 = 2^4 × 3 × 5
C.m.m.d.c.(120,180,240) = 2^2 × 3 × 5 = 60
b) 15 = 3 × 5
35 = 5 × 7
45 = 3^2 × 5
C.m.m.d.c.(15,35,45) = 5
c) 27 = 3^3
54 = 2 × 3^3
180 = 2^2 × 3^2 × 5
C.m.m.d.c(27,54,180) = 3^2 = 9
d) 144 = 2^4 × 3^2
156 = 2^2 × 3 × 13
192 = 2^6 × 3
C.m.m.d.c.(144,156,192) = 2^2 × 3 = 12