Question

( P_{n}=frac{n}{2}[2 a+(n-1) d]=(n-2)(pi) )
( frac{n}{2}[240+(n-1) 5]=(n-2)(1801 )
( 3-120 n+5 frac{n^{2}}{2}-frac{5 n}{2}=180 n-360 )
( -380+frac{5 n^{2}}{2}=55 n )
( -255 n^{2}-130 n+720=0 )
( n=8,18 )

# The interior angles of a convex polygon are in AP. The smallest angle is 120 & the common difference is 5. Find the number of sides of the polygon - A10 In

Solution