Question

How many of the following number are divisible by $3$ but not by $9?$
$2133,2243,3474,4131,5286,4340,6336,7347,8115,9276$

• A. $5$
• B. $6$
• C. $7$
• D. $4$

Answer 1

The correct option is D $4$

$\Rightarrow$ Divisibility by $3$ : The number will be divisible by $3$ if sum of the number is multiple of $3$.

$\Rightarrow$ Divisibility by $9$ : The number will be divisible by $9$ if sum of the number is multiple of $9$.

$\Rightarrow$ $2133=2+1+3+3=9$

$\Rightarrow$ $2243=2+2+4+3=11$

$\Rightarrow$ $3474=3+4+7+4=18$

$\Rightarrow$ $4131=4+1+3+1=9$

$\Rightarrow$ $5286=5+2+8+6=21$

$\Rightarrow$ $4340=4+3+4+0=11$

$\Rightarrow$ $6336=6+3+3+6=18$

$\Rightarrow$ $7347=7+3+4+7=21$

$\Rightarrow$ $8115=8+1+1+5=15$

$\Rightarrow$ $9276=9+2+7+6=24$

$\therefore$ We can see, $5286,6336,8115$ and $9276$ this numbers are divisible by $3$ but its its not divisible by $9$.

$\therefore$ Required number is $4$.