Question

(45+46+47+...+113+114+115)=? Please explain me in details

Answer 1

Answer:

a=45

d =1

an = 115

an=a+(n-1)d

115=45 + (n-1)1

115-45 = (n-1)

70 = n-1

n=71

Sn =n/2[2 a+(n-1)d]

Sn= 71/2[2*45+70*1]

Sn= 71/2(90-70)

Sn= 71/2(20)

Sn=71*10

Sn=710

(45+46+47+...+113+114+115)=710