Question

In the figure ABCD is a ||^gm in which ∠DAB = 80^o and ∠DBC = 60^o, then ∠CDB and ∠ADB are equal to

• A. ∠CDB = 60^o, ∠ADB = 80^o
• B. ∠CDB = 40^o, ∠ADB = 60^o
• C. ∠CDB = 30^o, ∠ADB = 70^o
• D. ∠CDB = 50^o, ∠ADB = 60^o

Answer 1

The correct option is B

∠CDB = 40^o, ∠ADB = 60^o

∠C = ∠A = 80^o (opposite angles of ||^gm)

In ∆CDB, ∠CDB = 180^o - (60^o + 80^o) = 40^o (By angle sum property of a triangle)

∠CDB = ∠DBC (alternate angles)

In ∆ADB, ∠ADB = 60^o (By angle sum property of a triangle)