Find Width of Rectangle with 600yd2 and 140yd Fencing

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Discussion Overview

The discussion revolves around determining the possible width of a rectangular enclosure given a fixed area of at least 600 yd² and a total fencing length of 140 yd. The constraints include that the width cannot exceed the length.

Discussion Character

  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant presents the problem and options for the width of the rectangle based on the given area and fencing constraints.
  • Another participant suggests using the relationship between length, $L$, and width, $(70-L)$, to derive constraints.
  • A different participant reformulates the problem in terms of width, stating that the inequality $(70 - w)w \ge 600$ must hold.
  • One participant proposes that the width must be less than the square root of 600, concluding that width 10 and length 60 meet the criteria.

Areas of Agreement / Disagreement

Participants express different approaches to the problem, and while some calculations and inequalities are presented, there is no consensus on the final limits for the width.

Contextual Notes

Participants reference various inequalities and conditions but do not resolve all mathematical steps or assumptions regarding the relationships between width and length.

alllove
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A rectangular enclosure must have an area of at least 600 yd2. If 140 yd of fencing is to be used, and the width cannot exceed the length, within what limits must the width of the enclosure lie?
Select one:
A. 35 ≤ w ≤ 60
B. 10 ≤ w ≤ 35
C. 10 ≤ w ≤ 60
D. 0 ≤ w ≤ 10
 
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length, $L$ and width $(70-L)$

constraints ...

$70-L \le L$

$L(70-L) \ge 600$

see what you can do from here
 
Last edited by a moderator:
Since the problem specifically asks about "w", the width, I would, instead, say that $(70- w)w\ge 600$.

Of course that's exactly the same as the inequality skeeter gave for L. There will be two solutions. It is the condition that "the width cannot exceed the length" that allows you to distinguish between them.
 
Width being less than square root of 600 I see that it is less than 25 so I have only one candidate d to check and width 10 so length 60 meets the criteria and hence the answer
 

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