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May 6th, 2017, 06:43 AM   #1
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Q19

How to solve question 19
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May 6th, 2017, 12:54 PM   #2
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Have you drawn a diagram that's roughly to scale?
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May 6th, 2017, 03:10 PM   #3
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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...
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May 6th, 2017, 05:14 PM   #4
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It turns out that 2r = 8 4/7 m.
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May 6th, 2017, 06:35 PM   #5
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So if the 3 circles had diameters of 210, 140 and 70,
then cut-out circle = diameter 60
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May 8th, 2017, 12:28 PM   #6
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Quote:
Originally Posted by skipjack View Post
Have you drawn a diagram that's roughly to scale?
that's hilarious. isn't this a math forum?
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May 8th, 2017, 12:36 PM   #7
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Quote:
Originally Posted by InkSprite View Post
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?
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May 8th, 2017, 01:26 PM   #8
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Oh. I thought you were telling him to guesstimate.
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May 8th, 2017, 01:44 PM   #9
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I'm sure skipjack was giving him an appropriate hint...

Last edited by skipjack; May 9th, 2017 at 01:45 AM.
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May 9th, 2017, 01:44 AM   #10
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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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