2021 · Q30
A person wishes to fence 375 m² rectangular garden. He has 65 m of barbed wire and is able to fence only three sides of the garden. What is the perimeter of the garden ?
Elementary MathematicsMensuration
- A80 m
- B84 m
- C90 m
- D100 m
Explanation
Let the fenced three sides be l + 2b = 65 with area lb = 375. Then b(65 − 2b) = 375 gives 2b² − 65b + 375 = 0, so b = 25 or 7.5, with l = 15 or 50. The 15 × 25 garden has perimeter 80 m, which is option (a). (The 50 × 7.5 alternative would give perimeter 115 m, which is not listed.)