waecmaths question:
In the diagram, PQ is a straight line, calculate the value of angle labelled 2y
Option A:
130o
Option B:
120o
Option C:
110o
Option D:
100o
waecmaths solution:
$\begin{align} & {{80}^{\circ }}+{{50}^{\circ }}+x+{{10}^{\circ }}={{180}^{\circ }}\text{ }\!\!\{\!\!\text{ Sum of angles on a straight line }\!\!\}\!\!\text{ } \\ & x={{40}^{\circ }} \\ & \text{Also,} \\ & 2y+2x={{180}^{\circ }}\text{ }\!\!\{\!\!\text{ Sum of angles on a straight line }\!\!\}\!\!\text{ } \\ & 2y+2({{40}^{\circ }})={{180}^{\circ }} \\ & 2y={{100}^{\circ }} \\\end{align}$
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