SAT Math Multiple Choice Question 945: Answer and Explanation

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Test Information

Question: 945

13. What is the value of?

  • A. -i
  • B. i
  • C. -1
  • D. 1

Correct Answer: C



Difficulty: Easy

Category: Additional Topics in Math / Imaginary Numbers

Strategic Advice: Powers of i cycle in the pattern i, -1, -i, 1. Memorizing this pattern may save you valuable time on Test Day. To determine the value of a high power of i, divide the exponent by 4 (the number of terms in the cycle). The remainder tells you which term in the pattern is the answer. For example, i11 = i3 because.

Getting to the Answer: When 48 is divided by 4, the remainder is 0; therefore, i48 = i4, which is 1. Don't forget about the negative sign in front of it, though. This makes the correct answer -1, which is (C).

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