Answer: 4 boxes.
Step-by-step explanation:
We know that each box has 18 ounces of cereal.
We know that:
1 lb = 16 oz
Then:
1 = (1lb/16oz)
Then we can write:
18 oz = 18oz*(1lb/16oz) = (18/16) lb
This means that each box has (18/16) pounds of cereal.
Now, how many boxes we need to buy if we want to have at least 4 pounds of cereal?
If we buy N boxes, we will have N*(18/16) lb boxes of cereal.
Let's find N such that:
N*(18/16) lb = 4lb
N = 4*(16/18) = 3.56
But you can not have a 0.56 of a box, so we should round our number up to the next whole number, then we get:
N = 4.
She should buy 4 boxes.
