Deposited energy over mass sets unshielded and shielded dose. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Three kilograms turns twelve joules into four
Before shielding, 12 joules over 3 kilograms gives dose 4 joules per kilogram. After shielding, 3 joules gives 1 joule per kilogram.
12÷3=43÷3=1
More energy and mass can keep the dose
Before shielding, 20 joules over 5 kilograms gives dose 4 joules per kilogram. After shielding, 5 joules gives 1 joule per kilogram.
20÷5=45÷5=1
Same mass with more energy raises dose
Before shielding, 18 joules over 3 kilograms gives dose 6 joules per kilogram. After shielding, 6 joules gives 2 joules per kilogram.