the 3rd term of an A.P is 6 and the 16th term is 32 find the common difference and the sum of the first 20 term
6 + thirteen d's = 32
13d = 26
d = 2
3rd term is 6 next is 8 10 12 14 16 18 20 22 24 26 28 30 32=16th term
1st term is 6 - 2 -2 = 2
Sumn = n/2 (a1 + an)
= 20/2 (2 + 40) = 420