For solid cylinder: I=21mR2
Large cylinder: mass m1=ρπR2L, so I1=21ρπR2L×R2=2ρπR4L
Small cylinder (carved out): length L/2, radius R/3, mass m2=ρπ(R/3)2(L/2)=18ρπR2L
I2=21×18ρπR2L×(R/3)2=21×18ρπR2L×9R2=324ρπR4L
I2I1=ρπR4L/324ρπR4L/2=2324=162