Two positive numbers have sum 20. What is the maximum possible value of their product?
Correct answer: C. 100
- A. 50
- B. 80
- C. 100
- D. 200
Explanation
If the numbers are x and 20 - x, their product is x(20 - x), a downward-opening quadratic. Its maximum occurs at x = 10, giving 10 × 10 = 100.
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