Question 1144667
<br>
The planting scheme is still not described clearly enough.<br>
The two answers from other tutors simply calculate how many square hills 3 feet 6 inches on a side will fit in an acre.  That interpretation means the hills are all adjacent to each other -- which means they aren't hills at all.<br>
With rows 3 feet 6 inches apart, and the hills 3 feet 6 inches apart (in each row), I think the arrangement of the hills ("XXXXX") looks something like this (pardon the crude text "drawing"):<br><pre>

    +-----+-----+-----+-----+-----+-----+-----+
 ...|XXXXX|     |XXXXX|     |XXXXX|     |XXXXX|  <-- row; hills 3'6" apart
    +-----+-----+-----+-----+-----+-----+-----+
    |     |     |     |     |     |     |     |  <-- 3'6" between rows
    +-----+-----+-----+-----+-----+-----+-----+
 ...|XXXXX|     |XXXXX|     |XXXXX|     |XXXXX|  <-- row; hills 3'6" apart
    +-----+-----+-----+-----+-----+-----+-----+
    |     |     |     |     |     |     |     |  <-- 3'6" between rows
    +-----+-----+-----+-----+-----+-----+-----+
 ...|XXXXX|     |XXXXX|     |XXXXX|     |XXXXX|  <-- row; hills 3'6" apart
    +-----+-----+-----+-----+-----+-----+-----+
    |     |     |     |     |     |     |     |  <-- 3'6" between rows
    +-----+-----+-----+-----+-----+-----+-----+
 ...|XXXXX|     |XXXXX|     |XXXXX|     |XXXXX|  <-- row; hills 3'6" apart
    +-----+-----+-----+-----+-----+-----+-----+
                                                  etc....</pre>
With that scheme, it can be seen that 1/4 of the area of the field is hills where the plants are planted.<br>
So I would guess the desired answers are 1/4 the number of hills and therefore 1/4 the number of plants shown by the other two tutors.<br>
Area of each square: 3.5^2 = 12.25 square feet<br>
Number of squares of area 12.25 square feet each in an acre: 43560/12.25 = 3556<br>
Number of hills: 3556/4 = 889<br>
Number of plants: 889*3 = 2667