Question

The sum of the series 25 + 28 + 31 + ... + 100 i

Answer 1

A=25

d=28−25=3

an=100

an=a+(n−1)d

100=25+(n−1)(3)

100−25=(n−1)(3)

75=(n−1)(3)

75/3=(n−1)

25=(n−1)

25+1=n

26=n

using formula for Sn

=n/2(a+an)

=26/2(25+100)

=13(125)

=1625