Answer: Ian's calculation was wrong.
Explanation:
Given: the amount of fat in 4 cups of chicken soup=

Then, the estimated amount of fat in 1 cup of chicken soup=

Now, to divide 13 by 4 we can use estimation that 13 is near to 12 anhd 12 divided by 4 is 3.
Therefore, the estimated amount of fat in 1 cup of chicken soup =3
But Ian calculated that the amount of fat in 1 cup soup = 0.331 which is estimated to 0.
Therefore, Ian's calculation was wrong.