Algebra & Equations · Question 22 · Medium
If 4x + 3y = 31 and 2x − y = 3, what is the value of xy?
- 12
- 9
- 20
- 15
Answer and explanation
Answer: C. 20
Explanation: From the second equation y = 2x − 3. Then 4x + 6x − 9 = 31, so x = 4 and y = 5. xy = 20.
Previous: If x + y = 12 and xy = 35, what is the value of x² + y²? · Next: A positive number exceeds its positive square root by 30. What is the number?
Practise algebra & equations
Try a fresh set of algebra & equations questions with an explanation after every answer, free and without signing up: Algebra & Equations practice. Or sit a full placement mock test.
More algebra & equations questions
- One-third of a number is 12 more than one-fifth of it. What is the number?
- What is the product of the roots of 3x² + 5x − 12 = 0?
- If x + y = 12 and xy = 35, what is the value of x² + y²?
- A positive number exceeds its positive square root by 30. What is the number?
- Which quadratic equation has roots 3 and −5?
- A number greater than 1, added to its reciprocal, gives 26/5. What is the…
- If (x − 2)/(x + 3) = 3/4, what is the value of x?
- If α and β are the roots of x² − 6x + 7 = 0, what is the value of α² + β²?
- If x + y = 10, y + z = 14 and z + x = 12, what is the value of xyz?
- If 2^(x + 1) + 2^x = 48, what is the value of x?
More quantitative aptitude practice
Number System · HCF & LCM · Simplification · Percentages · Profit & Loss · Simple & Compound Interest · Ratio & Proportion · Averages
LogicWiz Exams home · All practice topics · Placement mock tests · Daily 10 challenge