ISEE Mathematics Achievement Question 10: Answer and Explanation

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Question: 10

10. If y is a non-zero number, which one of the following can NEVER be true?

  • A. = 12
  • B. = 12
  • C. = 13 – y
  • D. = 13 – y

Correct Answer: C

Explanation:

C

Choice (D) cannot be true because under PEMDAS, you may not distribute the square root to each term under the square root. Rather, you must find the difference between the terms and then take the square root.

Guess and check to find out what could be true. For choice (A), as = 12, try to come up with a y value that will make the value under the square root equal to 144. Setting y equal to 5 works. Repeat the process for choice (B); in this case, setting y equal to 25 works. For choice (C), = 13, so setting y equal to 12 works. Select choice (C).

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