Answer:
The cost of per ounce of oat cereal is $0.04 less than per ounce cost of rice.
Step-by-step explanation:
Given:
Cost of 15 ounces of oat cereal box = $3.90
Cost of 11 ounces of rice box = $3.30
To compare the unit prices of the the boxes.
Solution:
Using unitary method to find the unit prices:
If 15 ounce of oat box cost =$3.90
∴ 1 ounce of oat cereal would cost = 
∴ Per ounce cost of oat cereal = $0.26
If 11 ounce of rice box cost =$3.30
∴ 1 ounce of rice would cost = 
∴ Per ounce cost of rice = $0.3
Difference in unit costs of oat and rice = 
On comparing the the unit costs of oats and rice, we find out that the cost of per ounce of oat cereal is $0.04 less than per ounce cost of rice.