Question
Four digit numbers are formed using the digits $1 , 2 , 3, 4$ (repetition is allowed). The number of such four digit numbers divisible by $11$ is

Answer

c
$\mathrm{N}=\mathrm{xyz} \mathrm{w}$

$x+z=y+w=k$

$\mathrm{k}=2: \quad 1^{2}$

$\mathrm{k}=3: \quad 2^{2}$

$k=4: \quad 3^{2}$

$k=5: \quad 4^{2}$

$k=6: \quad 3^{2}$

$k=7: \quad 2^{2}$

$k=8: \quad 1^{2}$

$\Rightarrow$ Total $=44$

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