waecmaths question:
In the diagram, PQR is straight line (m + n) = 120o and (n + r) = 100o. Find (m +r)
Option A:
110o
Option B:
120o
Option C:
140o
Option D:
160o
waecmaths solution:
$\begin{align} & m+n+r={{180}^{\circ }} \\ & r={{180}^{\circ }}-(m+n)={{180}^{\circ }}-{{120}^{\circ }}={{60}^{\circ }} \\ & n+r={{100}^{\circ }} \\ & n+{{60}^{\circ }}={{100}^{\circ }} \\ & n={{40}^{\circ }} \\ & m+n={{120}^{\circ }} \\ & m+{{40}^{\circ }}={{120}^{\circ }} \\ & m={{80}^{\circ }} \\ & m+r={{80}^{\circ }}+{{60}^{\circ }}={{140}^{\circ }} \\\end{align}$
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