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Homework Help: Surds - Division & rationalising

  1. Sep 24, 2012 #1
    1. The problem statement, all variables and given/known data

    simplify 5√20 / 5√15

    2. Relevant equations

    express your answer as a surd

    3. The attempt at a solution

    Looking for someone to check my work

    1. multiply (5√20)/(2√15) by (√15/√15)

    2. Above gives (5√300)/30

    3. Simplify the topline to 5 √100 x √3

    4. answer (50√3) / 30

    I checked my answer using http://www.wolframalpha.com/input/?i=simplify+(5√20)/(2√15)

    says I should get 5/√3

    how do you go about working out the above answer

    thanks
     
    Last edited: Sep 24, 2012
  2. jcsd
  3. Sep 24, 2012 #2
    Show how you got from step 2 to step 3 and from step 3 to step 4.
     
  4. Sep 24, 2012 #3
    took a pic of my work
     

    Attached Files:

  5. Sep 24, 2012 #4

    Mark44

    Staff: Mentor

    You entered a different problem on wolframalpha. What you entered there was 5√20/(5√15)

    The answer you have above is correct but should be reduced.
     
  6. Sep 24, 2012 #5
    Yeah looks like I entered that wrong on the website

    so (50√3)/ 30 can be tided up by having the √3 on the bottom

    gives 150/(30√3)

    which gives 5/√3
     
  7. Sep 29, 2012 #6

    Mentallic

    User Avatar
    Homework Helper

    Usually when you get questions like rationalizing the denominator, it's customary to leave your answer without any surds in the denominator, so even though [itex]5/\sqrt{3}[/itex] looks neater, you should leave your answer as [itex]5\sqrt{3}/3[/itex]
     
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