1. The problem statement, all variables and given/known data A 200. kg sample of MgO is given (Notice 3 sig figs). How many kg of magnesium ions would there be? 2. Relevant equations %Mg = 62% %O = 38% 3. The attempt at a solution Just a quick question I had about significant figures. The sample of MgO given is 200.kg (3 sig figs). The percent composition of magnesium is 62% (2 sig figs). Therefore 62% of the 200.kg will be magnesium. (62%/100%)(200.kg) = (0.62)(200.kg) = 124kg, but because the answer must have 2 sig figs, the final answer would be 120kg ( This is my suspicion ). Notice if the kg of oxygen is calculated : (38%/100%)(200.kg) = (0.38)(200.kg) = 76kg. This answer already has 2 sig figs, so nothing needs to be changed. Now when added together : 120kg + 76kg = 196kg < 200.kg. Is this result a fault of the rules or a fault of my own?