Question

The staff at the community center make a rectangular skating pit every year. They use 100 meters of boarding to enclose it. So the area of the pit depends on the width undefined chooses. This rule describes how the area depends on the width

Width: area:
10 400
15 525
20 600
25 ?

Answer 1

For a width of 25, the length will also be 25, so the area is 25² = ...
  625.

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The rule is
  area = width×(50 -width)