chemistry question?

Question

With a plentiful supply of air, 3.0 parts carbon reacts with 8.0 parts oxygen to produce carbon dioxide. use this mass ratio to calculate how much carbon is required to produce 990g of carbon dioxide. the answer is 270 but how the hell this that happen?

Answer 1

Step 1: Find the % of Carbon by weight in CO2.
CO2 = 1 atom of Carbon (12) + 2 atoms of Oxygen (16).
Molar weight: 12 + 2 * 16 = 44
% Carbon = 12/44 = 3/11 (let's keep this fraction)

Step 2: Multiply the ratio of carbon by the weight of CO2 given.
990 g * 3/11 = 3 * 90 = 270 g Carbon (solution)