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:
[tex]P = 2(l + w)[/tex]
In this question, the perimeter is of 1 ft by 4.5, thus, [tex]l = 1, w = 4.5[/tex], and the perimeter is:
[tex]P = 2(1 + 4.5) = 2(5.5) = 11[/tex]
1 plant - 2/3 ft
x plants - 11 ft
Applying cross multiplication:
[tex]\frac{2x}{3} = 11[/tex]
[tex]2x = 33[/tex]
[tex]x = \frac{33}{2}[/tex]
[tex]x = 16.5[/tex]
At least 8 inches apart(can be more), thus she should buy at most 16 plants.
A similar problem is given at https://brainly.com/question/10489198