Question

quantos multiplos de 3 existem entre os numeros 111 e 777 ?

Answer 1

$\large\boxed{\begin{array}{l}\rm (114,117,\dotsc774)\\\rm a_n=a_1+(n-1)\cdot r\longrightarrow n=\dfrac{a_n-a_1}{r}+1\\\\\rm n=\dfrac{774-114}{3}+1\\\\\rm n=\dfrac{660}{3}+1\\\\\rm n=220+1\\\rm n=221\end{array}}$