Final answer:
The diagram that models the ratio in the story is A. If Jacob's grandma peeled 16 potatoes, then Jacob peeled 4 potatoes. Together they peeled 20 potatoes.
Step-by-step explanation:
The diagram that models the ratio in the story is A. In this diagram, Jacob is represented by 1 potato and his grandma is represented by 4 potatoes. This ratio of 1:4 shows that Jacob's grandma peeled 4 times as many potatoes as Jacob peeled.
If Jacob's grandma peeled 16 potatoes, then Jacob peeled 16 divided by 4, which is 4 potatoes. Therefore, together they peeled 16 + 4 = 20 potatoes.