Surds - Division & rationalising

  • Thread starter chuffy
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  • #1
chuffy
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Homework Statement



simplify 5√20 / 5√15

Homework Equations



express your answer as a surd

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:

Answers and Replies

  • #2
skiller
237
5
Show how you got from step 2 to step 3 and from step 3 to step 4.
 
  • #3
chuffy
23
0
took a pic of my work
 

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  • #4
36,191
8,172

Homework Statement



simplify 5√20 / 5√15

Homework Equations



express your answer as a surd

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)/(5√15)
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.
says I should get 2/√3

how do you go about working out the above answer

thanks
 
  • #5
chuffy
23
0
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.

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
 
  • #6
Mentallic
Homework Helper
3,798
94
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

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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