Answer:
120
Step-by-step explanation:
Given arithmetic sequence
3,5,7,9,.........,21
The first term a=3 & a common difference d=5−3=7−5=⋯=2
If there are n number of terms in the above A.P. then last term l=21 will be the nth term given as
l=a+(n−1)d
21=3+(n−1)2
n=10
hence the sum of given arithmetic progression (A.P.) up to 10 terms is given general formula
Sn=n2(a+l)
S10=102(3+21)
=120
