Question

Determine a soma dos multiplos de 3 entre 50 e 30

Answer 1

a₁ = 33

an = 48

r = 3

48 = 33 + (n - 1) . 3 ---- 48 - 33 = (n - 1) . 3 ----- 15 = (n - 1) . 3

n - 1 = 15/3 ---- n - 1 = 5 ----- n = 5 + 1 ------ n = 6

S₆ = [(33 + 48) . 6]/2 -------- S₆ = (81) . 3 ----- S₆ = 243