Question

quantos multiplos de 13 existem entre 1 e 1000

Answer 1

$\frac{1000}{13}=76.13+12$, logo há 76 múltiplos de 13.

Ou,

$PA(13, 26, 39, ... , 988) \\ a_n=a_1+(n-1)r \\ 988=13+(n-1).13 \\ 975=(n-1).13 \\ 75=n-1 \\ n=76$