Question

(45+46+47+.....113+114+115)=?​

Answer 1

an=a+(n-1)d

115=45+(n-1)1

115=45+n-1

115=44+n

n=115-44

n=71

Sum=n/2(a+an)

=71/2(45+115)

=71/2×160

=71×80

=5680