Using the perimeter of the rectangle, it is found that she should buy at most 16 plants.
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The perimeter of a rectangle of length l and width w is given by:

In this question, the perimeter is of 1 ft by 4.5, thus,
, and the perimeter is:

- Perimeter of 11 ft.
- The plants will be at least 8 inches = 2/3 feet apart along the perimeter, thus:
1 plant - 2/3 ft
x plants - 11 ft
Applying cross multiplication:




At least 8 inches apart(can be more), thus she should buy at most 16 plants.
A similar problem is given at brainly.com/question/10489198