Question

the sum of the series 1+3+5+7..up to 10 terms

Answer 1

here
a=1
d=t2-t1
=3-1
=2
tn=a+n-1d
=1+18
=19


tn=19

Answer 2

1+3+5+7+9+11+13+15+17+19 = 100
Here is your answer