Practice Quiz

SAT Math Practice Exam

Category - Mathematics - Hard

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In which of the following pairs are two numbers reciprocals of each other?I √5 and √5/5II √5 and -√5III 5 and 1/5
  1. I only
  2. I and II
  3. I and III
  4. II and III
Explanation
Answer: C -The reciprocal of m is 1/m and the product of two reciprocal numbers is 1. Apply this test for the three pairs:
I √5 x √5/5 = 5/5 = 1
II √5 x -√5 = -5
III 5 x 1/5 = 1
The first and the third pairs are reciprocal pairs.

Key takeaway: The sign √ indicates square root of a number. You can multiply and divide square roots just like you would any number. However you can not add or subtracts the same way.
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