Given:
The smaller size is 24 oz and cost $3.99.
The larger size is 64 oz and cost $6.99.
To find:
Which has the lower unit cost?
Solution:
The formula for unit cost is

The unit cost of smaller size is


The unit cost of larger size is


It is clear that, 0.10922 is less than 0.16625.
Therefore, the unit cost of larger size is lower.