SOLUTION: The length of a wall is 3m more than its witdh. If the area of the wall is less than 18m squared, What could be its lenght?

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Question 1186358: The length of a wall is 3m more than its witdh.
If the area of the wall is less than 18m squared,
What could be its lenght?

Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


The problem is far more easily solved informally than with formal algebra.

6 times 3 is 18, and 3 is 3 less than 6; so the maximum length is 6.

The minimum length is whatever value keeps the width positive; since the width is 3 less than the length, the minimum length is 3.

ANSWER: The length can be any x in the interval (3,6)

Note the length can't be 6, because the area has to be LESS THAN 18 square meters; and it can't be 3, because the width would be 0 and there would be no wall.

If formal algebra is required....

x = length
x-3 = width

The area (length times width) has to be less than 18:

x%28x-3%29%3C18
x%5E2-3x%3C18
x%5E2-3x-18%3C0
%28x-6%29%28x%2B3%29%3C0

Algebraically, the solution is x between -3 and 6....

But in the actual problem, since the width has to be positive (x-3>0 --> x>3), the real solution is that x is between 3 and 6.