Question

Ache a soma dos multiplos de 3 compreendidos entre 50 e 300.

Answer 1

a1 = 51
an = 297
r = 3
an = a1+(n-1)*3
297 = 51+(n-1)*3
297-51 = 3n-3
246+3 = 3n
3n =  249
n = 249/3
n = 81

Sn = (a1+an)*n/2
Sn = (51+297)*81/2
Sn = 348*81/2
Sn = 174*81
Sn = 14094