My Math Forum Q19

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May 6th, 2017, 05:43 AM   #1
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Q19

How to solve question 19
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 May 6th, 2017, 11:54 AM #2 Global Moderator   Joined: Dec 2006 Posts: 19,047 Thanks: 1618 Have you drawn a diagram that's roughly to scale?
 May 6th, 2017, 02:10 PM #3 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,597 Thanks: 843 Try this: draw circle diameter 30 with center A(15,15) draw circle diameter 20 with center B(10,15) draw circle diameter 10 with center C(25,15) Now draw cut-out circle diameter 2r with center D(x,y) such that it is tangent to all 3 circles above Draw triangle BCD; sides will be: CD = 5+r, BD = 10+r, BC = 15 Have fun... Thanks from Shubh Mehta
 May 6th, 2017, 04:14 PM #4 Global Moderator   Joined: Dec 2006 Posts: 19,047 Thanks: 1618 It turns out that 2r = 8 4/7 m.
 May 6th, 2017, 05:35 PM #5 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,597 Thanks: 843 So if the 3 circles had diameters of 210, 140 and 70, then cut-out circle = diameter 60
May 8th, 2017, 11:28 AM   #6
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Joined: Dec 2016
From: United States

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Math Focus: Abstract Simulations
Quote:
 Originally Posted by skipjack Have you drawn a diagram that's roughly to scale?
that's hilarious. isn't this a math forum?

May 8th, 2017, 11:36 AM   #7
Math Team

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Posts: 12,597
Thanks: 843

Quote:
 Originally Posted by InkSprite that's hilarious. isn't this a math forum?
Hey buddy, you never drew a "rough diagram"
in order to better understand a math problem?

 May 8th, 2017, 12:26 PM #8 Member   Joined: Dec 2016 From: United States Posts: 53 Thanks: 3 Math Focus: Abstract Simulations Oh. I thought you were telling him to guesstimate.
 May 8th, 2017, 12:44 PM #9 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,597 Thanks: 843 I'm sure skipjack was giving him an appropriate hint... Last edited by skipjack; May 9th, 2017 at 12:45 AM.
 May 9th, 2017, 12:44 AM #10 Global Moderator   Joined: Dec 2006 Posts: 19,047 Thanks: 1618 A good estimate suffices for this multiple choice question. The exact value can easily be found by use of this theorem.

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