The 10th and 15th term of an AP are -5 and 7.5 respectively what is the sum of first 20 terms
2 answers
The sum of the first 20 terms of the AP is -50.
d = 12.5/5 = 2.5
so a = -30
S20 = 20/2 (-30+19*2.5) = 175
so a = -30
S20 = 20/2 (-30+19*2.5) = 175