Question

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In ∆ABC, side BC has been produced to D. If ∠BAC = 45° and ∠ABC = 55°, then ∠ACD = ?



(a) 80°
(b) 90°
(c) 100°
(d) 110°

Answer 1

$$\begin{gathered} \left(\mathrm{c}\right)100° \\ \begin{array}{l}\angle \text{ACB}=\angle \text{ABC+}\angle \text{BAC (exterior angle property)}\\ \text{=}(45°+55°)\\ \text{=100}°\\ \\ \end{array} \end{gathered}$$