Question

Qual é a Soma dos múltiplos de 5 compreendido entre 9 e 109?

Answer 1

$> resolucao \\ \\ \geqslant progressao \: \: aritmetica \\ \\ an = a1 + (n - 1)r \\ 105 = 10 + (n - 1)5 \\ 105 = 10 + 5n - 5 \\ 105 = 5 + 5n \\ 105 - 5 = 5n \\ 100 = 5n \\ n = \frac{100}{5} \\ n = 20 \\ \\ = = = = = = = = = = = = = = = = \\ \\ \\ sn = \frac{(a1 + an)n}{2} \\ \\ sn = \frac{(10 + 105)20}{2} \\ \\ sn = \frac{115 \times 20}{2} \\ \\ sn = 115 \times 10 \\ \\ sn = 1150 \\ \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \geqslant \geqslant \leqslant \geqslant \geqslant$