Basic things derived from what's given:
OC = OB (=> OBC = BCO)
AB = OC
=> AB = OB
=> BAO = BOA
(1)
COD = 60
=> BAO + BCO = 60
=> BAO + OBC = 60
Because BAO + BOA = OBC (basic property of triangle)
And recall that BAO = BOA
=> 2BAO = OBC
=> BAO + 2BAO = 60
=> 3BAO = 60
=> BAO = 20
(2)
BCO = 40
=> OBC = 40
Because BAO + BOA = OBC (basic property of triangle)
=> BAO + BOA = 40
Because BAO = BOA
=> BAO = BOA = 20
Each statement alone is sufficient.
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Source: Beat The GMAT — Data Sufficiency |
