Math
posted by Punkie .
The two cereal boxes shown have corresponding edges in a ratio of 2:3. If the smaller box sells for $2.50 and the larger box for $4.00, which is the better buy? Why? What assumption(s) do you have to make when solving the problem? Estimate, then check.
Could someone show me how to solve this? I don't know what formulas to use.

what is 1/2  1/2
Im doing modeling subtraction of fractions 
hint:
The volumes of the two similar boxes are proportional to the cubes of their corresponding sides.
so the larger box:smaller box = 27:8
so the larger holds over 3 times as much as the smaller.
Now look at the cost.