# Ratio and proportion 2

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• October 17th 2009, 05:42 AM
Aminekhadir
Ratio and proportion 2
Hello!
This is a question about ratio and proportion.
Attachment 13400

When I solve the question I get the answer to be sqrt21, which isn't correct. The correct answer is a).
I would appreciate your help :)
Thanks,
Amine.
• October 17th 2009, 05:57 AM
mathaddict
Quote:

Originally Posted by Aminekhadir
Hello!
This is a question about ratio and proportion.
Attachment 13400

When I solve the question I get the answer to be sqrt21, which isn't correct. The correct answer is a).
I would appreciate your help :)
Thanks,
Amine.

HI

$a+b=\sqrt{(1-\sqrt{5})^2}+\sqrt{(\sqrt{5}-\sqrt{20})^2}$

$=|1-\sqrt{5}|+|\sqrt{5}-\sqrt{20}|$

$=|1-\sqrt{5}+\sqrt{5}-\sqrt{20}|$

$=|1-\sqrt{20}|$

$=1-\sqrt{20}$ or $\sqrt{20}-1$

Since it must be positive , then take $\sqrt{20}-1$