Posted by G on .
Dividing Radicals
I used this for the redial sign \/
Problem:
30 \/15
_______
4 \/10
The book says the answer is 15/4 \/6 (15/4 with radicand of 6). I have tried to solve the problem several different ways. I do not arrive at this answer.

Algebra 
Reiny,
how about this :
30√15 / (4√10)
= 15√3 / 2√5 now multiply top and bottom by √2
= 15√6 /4 
Algebra 
G,
Thank you for your response.
I did get 15\/3 and 2\/5. Why would you then mutiply by \/2?
The answer in the book is 15/4 with radicand of 4 not a radicand of 6. Are you also showing that there is a missprint in the book and the racdicand is 4?
I have several missprints int he book. 
Algebra 
Reiny,
At the top of your post you said the book answer was 15/4 with radicand of 6
and now you say it is 15/4 with radicand of 4 not a radicand of 6. ???
It is generally considered "poor form" to have a radical in the denominator
This goes back to precalculator times.
What would you rather have done back in 1950:
divide by √2 which would be dividing by 1.4142136...
or divide by 4 ? 
Algebra 
Reiny,
BTW, I just noticed that my second last line in my solution is
15√3 / 2√5
that should have been
15√3 / 2√2 
Algebra 
G,
If is 4 \/10. Why would it be 2 \/2 and not the 2 \/5?

Algebra 
Reiny,
OK, from the start:
30√15 / (4√10) divide top and bottom by 2√5
= 15√3 / 2√2 multiply top and bottom by √2
= 15√6 /4