Question:
ind all possible values of x for which the number 7x3 is divisible by 3. Also, find each such number.
Solution:
For a number to be divisible by 3, the sum of the digits must be divisible by 3.
Sum of the digits $=7+x+3$
$=10+x$
$10+x$ will be divisible by 3 in the following cases:
$10+x=12$, or $x=2$
Thus, the number will be 723 .
$10+x=15$, or $x=5$
Thus, the number will be 753 .
$10+x=18$, or $x=8$
Thus, the number will be 783 .
So, the numbers can be 723, 753 or 783.