19. (6 points) A 30 cm long iron wire can form $\qquad$ different rectangles (with side lengths in whole centimeters).
【Answer】Solution: The perimeter of a rectangle $=($ length + width $) \times 2$,
The sum of length and width is: $30 \div 2=15$ (cm),
Since $15=1+14=2+13=3+12=4+11=5+10=6+9=7+8$, we can form 7 different rectangles.

Answer: We can form 7 different rectangles.
Therefore, the answer is: 7.