Question

Calcule a soma da PA (2, 4,..., 200).

Answer 1

An = 200

a₁ = 2

n = ?

r = a₂  - a₁

r = 4 - 2

r = 2

An = a₁ + (n - 1) * r

200 = 2 + (n - 1) * 2

200 = 2 + 2n - 2

200 = 2n

n = 200/2

n = 100

Sn = (a₁ + an) * n / 2

S₁₀₀ = (2 + 200) * 100 / 2

S₁₀₀ = 202 * 50

S₁₀₀ = 10 100

Answer 2

Sn= [(2+200)x100]/2

Sn= 10100