Question

find the sum of the series 3 + 7 + 11 + ...to 10th terms​

Answer 1

this is an A.P with first term=a=3 n=10 and common difference=d=7-3=4

sum up to nth terms = n/2{2a+(n-1)d}

sum up to 10 terms = 10/2{2*3+ 9*4}=210

Answer 2

a=3

d=7-3=4

n=10

l=10th term a+9d

3+9(4)

3+36

39

..

..

Sum=n/2(a+l)

=10/2(3+39)

=5(42)

=210