Question 20

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waecmaths question: 

The interior angle of a pentagon are (2x + 5)o, (x + 20)o, xo, (3x – 20)o and (x + 15)o. Find the value of x

Option A: 

80o 

Option B: 

70o

Option C: 

65o

Option D: 

40o

waecmaths solution: 

The sum of angles in a pentagon is 540o$\begin{align}  & {{(2x+5)}^{\circ }}+{{(x+20)}^{\circ }}+{{x}^{\circ }}+{{(3x-20)}^{\circ }}+{{(x+15)}^{\circ }}={{540}^{\circ }} \\ & {{(8x+20)}^{\circ }}={{520}^{\circ }} \\ & x={{65}^{\circ }} \end{align}$

maths year: