The exterior angles obtained on producing the base BC of

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The exterior angles obtained on producing the base BC of a triangle ABC in both ways are 120° and 105°, then the vertical ∠A of the triangle is of measure

1. 36°
2. 40°
3. 45°
4. 55°

Correct Option: C

As per the given in question , we draw a figure of triangle ABC ,

∠ABD = 120°
∴ ∠ABC = 180° – 120° = 60°
∠ACE = 105°
⇒ ∠ACB = 180° – 105° = 75°
∴ ∠BAC = 180° – 60° – 75° = 45°