Question

If x is a digit such that the number $\overline{18x71}$ is divisible by 3, find possible vaues of x.

Answer 1

$\because$ The number $\overline{18x71}$ is divisible by 3
$\therefore$ The sum of digits will also be divisible by 3
$\Rightarrow$ 1+ 8 + x + 7 + x 1 is divisible by 3
$\Rightarrow$ 17+x is divisible by 3
The sum grerater than 17, can be 18,21,24,27..............
$\therefore$ x can be 1,4,7 which are divisible by 3.