clearly T16 = 1464-1290 = 174
16/2 (a+174) = 1464
a = 9
T16 = 9+15d = 174
d=11
S20 = 20/2 (2*9+11*19) = 2270
The sum of the first 15 terms of an arithmetic series is 1290. The sum of the first 16 terms is 1464.
Find t16? Find S20
1 answer
1 answer