Question

two cereal boxes 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.

Answer 1

assumption: The cost of the cereal should be directly proportional to the volume.

volume(smaller):volume(larger) = 2^3:3^3 = 8:27

Let the volume of the smaller be 8x units
let the volume of the larger be 27x units

unit cost of smaller box = 2.5/(8x)
= .3125/x
unit cost of larger box = 4/27x
= .148/x

clearly the larger box is the better buy.