Question

Find the sum of the sequence 45+46+47+48+.... +124

Answer 1

Answer:

$\boxed{6760}$

Step-by-step explanation:

The formula for the first n terms of an arithmetic sequence is

Sₙ = n(a₁+ aₙ)/2

1. Find the number of terms

n = (124 - 45) + 1 = 79 + 1 = 80

2. Find the sum

 a₁ =   45

a₈₀ = 124

$S_{80} = 80 \left(\dfrac{45 + 124 }{2}\right) = 80 \times 84.5= \boxed{\mathbf{6760}}$