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Angles on a Line

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Angles on a Line

by hansoo » Sat Sep 12, 2009 3:32 pm
If a = (d/4), c = a - 20, and 2a = b, then what is the value of b?

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a) 20
b) 25
c) 35
d) 40
e) 50
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by truplayer256 » Sat Sep 12, 2009 3:42 pm
a+b+c+d=180

a=d/4-->b/2=d/4-->d=2b

c=a-20-->c=b/2-20

2a=b-->a=b/2


b/2+b+b/2+2b=200

4b=200

b=50
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by Nermal » Sun Sep 13, 2009 2:03 am
IMO E (50)

You can express the equation a+b+c+d=180 in terms of a only.

a+4a+a-20+2a=180
8a-20=180
8a=200
a=25
b=2a=2*25=50
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by grockit_jake » Sun Sep 13, 2009 9:27 am
a = (d/4)
c = a - 20
and 2a = b
a + b +c + d = 180

Now just replace b, c, d in terms of a and solve.
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by hansoo » Sun Sep 13, 2009 6:02 pm
Nice job guys! The official answer is E.

Here's a video explanation: GMAT video

And here's a text explanation:


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