Advanced MathHardTwo numbers from a sum and a sum of squares
Advanced Math practice question
Two positive numbers have a sum of 7 and a sum of squares of 25. What is the product of the two numbers?
Answer: 12
(x + y)² = x² + 2xy + y², so 49 = 25 + 2xy and xy = 12. (The numbers are 3 and 4.)
Common wrong answers
- If you answered 7
- 7 is the sum, not the product.
- If you answered 24
- 24 is 2xy, forgetting to halve.
- If you answered 25
- 25 is the sum of squares, not the product.
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