Question

7. A soma dos múltiplos de 10, compreendidos entre 1 e 2000, é: a) 201 000 b) 20 100 c) 200 000 d) 210 000 e) 2 001 000 7.​

Answer 1

$> resolucao \\ \\ \geqslant progressao \: aritmetica \\ \\ an = a1 + (n - 1)r \\ 1990 = 10 + (n - 1)10 \\ 1990 = 10 + 10n - 10 \\ 1990 = 10n \\ n = \frac{1990}{10} \\ n = 199 \\ \\ = = = = = = = = = = = = = = = = = = \\ \\ > soma \: dos \: termos \: da \: pa \\ \\ sn = \frac{(a1 + an)n}{2} \\ \\ sn = \frac{(10 + 1990)199}{2} \\ \\ sn = \frac{2000 \times 199}{2} \\ \\ sn = 1000 \times 199 \\ \\ sn = 199000 \\ \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \geqslant$