circle problem

A

apple2357

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Mar 9, 2018
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1586616626868.png

Can anyone offer some hints with this one..? I am thinking symmetry, can't see any similar triangles, see a right angle too. But do i need to make some assumptions here. Just a hint would do!
 
Draw in as many radii as you can, for each circle; maybe name the radii x, y, z, and look for relationships. Pythagoras should be helpful/
 
I am entirely convinced by my reasoning just yet but I’d appreciate it if someone could tell me if my answer is correct. I get 0.5

Ignore that.. i made a schoolboy error..
 
Last edited:
Consider this diagram:

fmh_0135.png

Can you express \(r_3\) in terms of \(r_1\)?
 
Thanks Mark. I did something similar in the end. For some reason, i used the angle in a semi-circle was a right angle but it wasn't necessary. I got an answer of 1/3 which looks about right too!
 
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