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XAT 2016 — QA & DI Question 6

Basics of TrianglesEasy

In the figure below, AB = AC = CD. If ∠ADB = 20°, what is the value of ∠BAD?

Answer & solution

  • A

    40°

  • B

    60°

  • C

    70°

  • 120°

  • E

    140°

Solution

In ∆ ACD, AC = CD 
⇒ ∠CAD = ∠CDA = 20°

In ∆ ABC
∠ACB = ∠CAD + ∠CDA = (20 + 20)° = 40°   …(Exterior angle theorem)

Also, AC = AB 
⇒ m∠ABC = ∠ACB = 40°

∴ m∠BAD = 180 – 40 – 20 = 120°

Hence, option (d).

XAT 2016 QA & DI Q6: In the figure below, AB = AC = CD. If ∠ADB = 20°, what is the value of ∠BAD? — Solution | TheCATExam