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19 Aug 2007, 06:50
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N
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Please explain the answer
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19 Aug 2007, 07:42
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The answer is D.
It's useful to label all given information first.
You know:
AB = OB = OC
Angle BAO = BOA --> label this angle a
Angle OBC = OCB --> label this angle x
Angle ABO --> label this angle b
angle BOC --> label this angle y
angle COD --> label this angle z
(We want to solve for angle a)
From this:
2x+y = 180
2a+b = 180
2a+x+y = 180
a+y+z = 180
b+x = 180
solvable:
2a = x
Now, plug in statement 1:
COD (z) = 60
a+y+60 = 180
a+x = 60
a+2a = 60
3a = 60
a = 20
Sufficient.
Now, plug in statement 2:
BCO (x) = 40
we already know that 2a=x, therefore, a = 20
Sufficient.
It's useful to label all given information first.
You know:
AB = OB = OC
Angle BAO = BOA --> label this angle a
Angle OBC = OCB --> label this angle x
Angle ABO --> label this angle b
angle BOC --> label this angle y
angle COD --> label this angle z
(We want to solve for angle a)
From this:
2x+y = 180
2a+b = 180
2a+x+y = 180
a+y+z = 180
b+x = 180
solvable:
2a = x
Now, plug in statement 1:
COD (z) = 60
a+y+60 = 180
a+x = 60
a+2a = 60
3a = 60
a = 20
Sufficient.
Now, plug in statement 2:
BCO (x) = 40
we already know that 2a=x, therefore, a = 20
Sufficient.
