Question:
Tick (✓) the correct answer:
The angles of a pentagon are x°, (x + 20)°, (x + 40)°, (x + 60)° and (x + 80)°. The smallest angle of the pentagon is
(a) 75°
(b) 68°
(c) 78°
(d) 85°
Solution:
(b) 68°
Sum of all the interior angles of a polygon with $n$ sides $=(n-2) \times 180^{\circ}$
$\therefore(5-2) \times 180^{\circ}=x+x+20+x+40+x+60+x+80$
$\Rightarrow 540=5 x+200$
$\Rightarrow 5 x=340$
$\Rightarrow x=68^{\circ}$