Question

(PORTAL DA MATEMÁTICA) Qual a soma dos múltiplos de 7 compreendidos entre 1 e 100?

a) 735
b)700
c) 145
d) 155
e) 853 ​

Answer 1

Resposta:

a) 735

Explicação passo a passo:

$a_{1} =7\\\\r=7\\\\a_{n} =98\\\\n=\ ?\\\\S_{n} =\ ??$

$a_{1} +(n-1)\times r=a_{n}\\\\7 +(n-1)\times 7=98\\\\1\times7+(n-1)\times7=98\\\\(n-1+1)\times7=98\\\\n\times7=98\\\\n=\frac{98}{7} \\\\n=14$

$S_{n} =\frac{(a_{1} +a_{n} )\times n}{2} \\\\S_{14} =\frac{(7 +98 )\times 14}{2} \\\\S_{14} =\frac{105\times 14}{2}\\\\S_{14} =105\times 7\\\\S_{14} =735$

Answer 2

Letra a)735
7+14+21+28+35+42+49+56+63+70+77+84+91+98