Answer:
C (√10)/2
Explanation:
Multiply numerator and denominator by √10. Then you have ...
... (5√10)/10 = (√10)/2
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Of course, you can always compare the given answers by using your calculator.
5/√10 ≈ 1.58114
The answer choices are ...
... A: 1.41421
... B: 2.23607
... C: 1.58114 . . . . matches the given expression in value
... D: 0.707107
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If you're familiar with the square roots of small integers, you can do this last exercise in your head once you have calculated 5/√10. That is, you can eliminate choices A, B, and D.
... √2 ≈ 1.414; √3 ≈ 1.732; √5 ≈ 2.236