SAT Math Multiple Choice Question 112: Answer and Explanation

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Question: 112

7. If 3a + 2b = 24 and 4a + 5b = 53, what is the value of a + b ?

  • A. 2
  • B. 7
  • C. 9
  • D. 11

Correct Answer: D


DThis question requires evaluating both equations to determine the values of a and b. You could begin by solving either of the two equations for a or b, and then substituting the solution into the other equation. But note that the question asks for the value of a + b, so check to see if there's a faster way: Could you stack and add (or subtract) the equations? If you stack and add the equations, you get 7a + 7b = 77. Now divide both sides of the equation by 7, resulting in a + b = 11. This is (D).

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