Question

calcule a soma dos multiplos de 7 compreendidos entre 100 e 300.

Answer 1

a1=105
an=294
n=?
razão=7

an=a1+(n-1).r
294=105+(n-1).7
294=105+7n-7
294+7-105=7n
n=196/7
n=28


Soma:

sn=(a1+an).n/2
s28=(105+294).28/2
s28=399.14
s28=5586