Let AB and CD be two lines intersecting each other at O. If the ratio of ∠COB and ∠AOC is 5:4, then the measure of ∠AOD will be
100o
∠COB and ∠AOC form a linear pair of angles.
Let the angles be ∠COB = 5x and ∠AOC = 4x.
Then 5x + 4x = 180o or x = 20o
Thus ∠COB = 100o and ∠AOC = 80o.
Now, ∠COB and ∠AOD form a pair of vertically opposite angles.
Hence ∠AOD = ∠COB = 100o