Question

A 3 lb bag of one brand of cat food costs $3.52. A 6 lb bag of another brand costs $6.80. Which brand is cheaper per pound?

Answer 1

A 6 lb bag of another brand 

Answer 2

For this case what we should do is find the price per pound of each of the brands of cat food.
We have then:
Mark 1:
3 lb costs $ 3.52
P = (3.52) / (3) = 1.17 $ / lb
Mark 2:
6 lb costs $ 6.80
P = (6.80) / (6) = 1.13 $ / lb
Answer:
Mark 2 is cheaper per pound:
1.13 $ / lb