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Angle Basics, SM-Bank 018

A straight line, as shown below, is split into three angles.
 

Calculate the value of \(a^{\circ}\), giving reasons.   (2 marks)

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\(\text{Straight lines have 180}^{\circ}\ \text{about a point.}\)

\(a^{\circ} = 30^{\circ}\)

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\(\text{Straight lines have 180}^{\circ}\ \text{about a point.}\)

\(a+3a+2a\) \(=180\ \ \text{(supplementary angles)}\)  
\(a^{\circ}\) \(=\dfrac{180}{6}\)  
  \(=30^{\circ}\)