Question

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

Answer 1

`\boxed{6760}`

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((45 + 124 )/(2)\right) = 80 * 84.5= \boxed{\mathbf{6760}}`