$$1.72\times2=3.44$$  $$3.44 -1.68 = 1.76$$  The mass of the other bag of flour is $$1.76\text{kg}$$. 
The average mass of $$2$$ bags of flour is $$1.72 \text{kg}$$. The mass of one of the bag of flour is $$1.68 \text{kg}$$. What is the mass of the other bag of flour? 
  $$1.76kg$$ 
  $$3.44kg$$ 
  $$1.68kg$$ 
  $$1.72kg$$ 