Calculate how many mg is lethal to resident arnold who weighs 45 kg and resident harold who weighs 96 kg. the ld50 of lead is 450 mg/kg

To get the answer, use the value that has two units because that's your conversion factor (what is used to convert).

conversion factor--> 450 mg/Kg
this value tells us that 450 mg= 1 Kg
use it so the units cancel (what you converting from in the denominator, Kg, what you converting to in the numerator, mg)

Arnold

45 Kg x (450 mg/ 1 kg)= 20250 mg

Harold

96 Kg (450 mg/ 1 Kg)= 43200 mg