Question

(3) Here interior angle - exterior angle ( =60^{circ} ) sol.
( frac{(n-2) times 180^{circ}}{n}-frac{360^{circ}}{n}=60^{circ} )
( frac{1}{n}left[(n-2) times 180^{circ}-360^{circ}right]=60^{circ} )
( frac{1}{n}left[180^{circ} n-360^{circ}-360^{circ}right]=60^{circ} )
( frac{1}{n}left[180^{circ} n-720^{circ}right]=60^{circ} )
( 180^{circ} n-720^{circ}=60^{circ} n )
( 120^{circ} n=720^{circ} )
( n=frac{720^{circ}}{120^{circ}}=6 )

# Ez.3. The difference between the interior and exterior angles of a regular polygon is 60°. The number of sides of the polygon is : (1) 4 (2) 5 (3) 6 (4) 8

Solution