An attenuation rate scan shows how radiation rate drops with distance or shielding, comparing inverse-square spreading with half-value-layer absorption. The three rows give rate 80/s dropping to 20/s over doubled distance, 64/s halving three times to 8/s through shielding, and 100/s dropping to 25/s exactly for the stated toy rate ledger; real shielding measurements depend on spectrum, geometry, detector calibration, background subtraction, and finite-count uncertainty.
Distance spreading and half-layers reduce checked count rates. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Doubling distance quarters the rate
Rate 80 per second at distance 2 metres becomes 20 per second at distance 4 metres.
80÷4=20
Three half-layers divide by eight
3 half-value layers turn 64 per second into 8 per second.
64→32→16→8
A second distance doubling also quarters
Rate 100 per second at distance 3 metres becomes 25 per second at distance 6 metres.