A farmer has 100 m of fence and builds a rectangular pen against a long straight wall, so only three sides need fencing. What is the largest area?
Answer and explanation
Correct answer: C.
- Step 1: Let the two sides at right angles to the wall be . The side along the wall is , so the area is . Step 2. The maximum is at , where the area is . **Answer: . Why not the others:** would use all four sides as a square of side 50, uses a square of side 25, and is not the maximum.
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