Question

quantos multiplos de cinco existem de 170 a 280​

Answer 1

PA: (175, 180, 185....275)
n=(an-a1/r) +1
n=(275-175/5) +1
n= (20) +1 = 21 ✓

a1 +(n-1).r = an
175 +(n-1).5 = 275
(n-1).5 = 275 -175
(n-1).5 = 100
(n-1) = 100/5
n-1 = 20
n= 20+1
n=21