Question

Cate numere de forma 7ab sunt divizibile atat cu 2 cat si cu 3?

Answer 1

Numerele cerute trebuie sa fie  divizibile cu  6, deci $\overline{7ab}=6\cdot k, \ k\in N$

$700\leq6k\leq799$

$\dfrac{700}{6}\leq k\leq \dfrac{799}{6}$

$116,...\leq k\leq133,...$

$k\in\{117;118;...133\}$

$\overline{7ab}\in\{6\cdot117;\ 6\cdot118;\ ...\ ;\ 6\cdot133\}$