SAT Math Multiple Choice Question 31: Answer and Explanation

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Test Information

Question: 31

1. 20 - 2x

20 - x

20

20 + x

20 + 2x

What is the average (arithmetic mean) of the list of numbers above?

  • A. 20
  • B. 100
  • C. 20 +
  • D.

Correct Answer: A

Explanation:

A Variables in the answers? Plug in! Make up a value for x. Let's say that x is 3. The list of numbers then becomes 20 - 2(3), 20 - 3, 20, 20 + 3, 20 + 2(3), so the list is 14, 17, 20, 23, and 26. To find the average, make an average pie: We know the number of things (5) and the total (14 + 17 + 20 + 23 + 26 = 100), so the average is 100 รท 5 = 20, which is (A).

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