Expressing fractions as powers?

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Discussion Overview

The discussion revolves around expressing the fraction 125 over the square root of 5 as a power of 5. Participants explore methods and reasoning related to the laws of indices and the manipulation of exponents.

Discussion Character

  • Mathematical reasoning

Main Points Raised

  • One participant initially presents a question about expressing 127 over the square root of 5, but later corrects it to 125 over the square root of 5.
  • Another participant questions the original value of 127, noting that none of the provided multiple-choice answers match this value.
  • A participant explains that a number in the denominator corresponds to a negative exponent in the numerator, clarifying that the square root of 5 in the denominator translates to an exponent of -1/2.
  • There is a suggestion that if the denominator were the square root of 5 cubed, the exponent would be -3/2.
  • A later reply provides a step-by-step breakdown of the expression, showing that 125 can be rewritten as \(5^3\) and the square root of 5 as \(5^{1/2}\), leading to the conclusion that the expression simplifies to \(5^{5/2}\).

Areas of Agreement / Disagreement

Participants generally agree on the method of expressing the fraction as a power of 5, but there is some initial confusion regarding the correct numerator. The discussion remains focused on the mathematical manipulation rather than reaching a consensus on a single approach.

Contextual Notes

There is a dependency on the correct interpretation of the initial problem statement, which was clarified during the discussion. The resolution of the expression relies on the application of the laws of indices.

Who May Find This Useful

Students preparing for exams in mathematics, particularly those focusing on exponentiation and the manipulation of fractions.

MadmanMurray
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Expressing fractions as powers??

How would you go about expressing this 127/squareroot(5) as a power of 5? I got a copy of last years exams to use for revision and practice and its full of stuff I don't know how to do. This one happens to be a multiple choice and the possible answers are 5 to the power of A:3 1/2, B: 6, C: -1 1/2, D: -3

I know most of the laws of indices but I am stuck here.
 
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Are you sure the question says 127/squareroot(5)?

You can check that none of the answers match this value.
 


A number in the denominator corresponds to a number in the numerator with a negative power. However, sqrt(5) in the denominator is 5-1/2, not -1 1/2 or -3. If the denominator were [itex]\sqrt{5^3}= \sqrt{125}[/itex], then the exponent would be -3/2= -1 1/2.
 


Sorry it was 125 over square root of 5 not 127. I have no idea how to solve this.

I considered actually dividing the denominator into the numerator then using logs to convert the answer to a power of 5 but that method seems way too impractical to be the commonly used method.

HallsofIvy I don't fully get what you said about the denominator and the numerator.
 
Last edited:


Spelling it out,

[tex]\frac{125}{\sqrt{5}} = \frac{5^3}{5^{1/2}} = 5^{3 - 1/2} = 5^{5/2}[/tex]
 


Thanks a lot.
 

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