To find out how many barrels of tomatoes the farmers picked on Thursday, we need to calculate half of the amount picked on Wednesday.
On Wednesday, the farmers picked 9 barrels of tomatoes.
To find half of 9, we can perform the following calculation:
\[ \frac{1}{2} \times 9 = \frac{9}{2} \]
Now, we can convert \(\frac{9}{2}\) into a mixed number:
\(\frac{9}{2} = 4 \frac{1}{2}\) (this is because 9 divided by 2 equals 4 with a remainder of 1).
Thus, the farmers picked \(\frac{9}{2}\) barrels or \(4 \frac{1}{2}\) barrels of tomatoes on Thursday.
Therefore, the answer is: \[ \frac{9}{2} \text{ barrels} \] or \(4 \frac{1}{2} \text{ barrels}\)