SAT Math Multiple Choice Question 929: Answer and Explanation

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Question: 929

13. If (x, y) is a solution to the system of equations above, what is the value of y2?

  • A. 12
  • B. 16
  • C. 120
  • D. 144

Correct Answer: D



Difficulty: Medium

Category: Passport to Advanced Math / Quadratics

Strategic Advice: When you encounter a system of equations in which one of the equations is already solved for a variable, substitute its value into the other equation and solve.

Getting to the Answer: The second equation tells you that y is equal to 3x, so substitute 3x for y in the first equation. Then solve for x2 (not x because x2 will be more useful when solving for y2):

Now, substitute 16 for x2 in the first equation and solve for y2:

The correct answer is (D).

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