Moment of inertia changes linearly with mass and quadratically with radius. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
One-meter radius gives two inertia units
Mass 2 kg at radius 1 m gives inertia 2 kilogram meter squared.
I=2×12=2
Doubling radius quadruples inertia
Mass 2 kg at radius 2 m gives inertia 8 kilogram meter squared.
I=2×22=8
Doubling mass doubles the already-squared row
Mass 4 kg at radius 2 m gives inertia 16 kilogram meter squared.