A man bought apples at 10 for ₹ 75 and sold them at ₹ 75 per dozen.

LCM of 10 and $12=60$

Let the number of apples bought be 60 .

CP of 10 oranges $=₹ 75$

$\therefore$ CP of 1 orange $=₹ \frac{75}{10}$

$\Rightarrow$ CP of 60 orange $=60 \times \frac{75}{10}=₹ 450$

SP of 12 oranges $=₹ 75$

$\therefore$ SP of 1 orange $=₹ \frac{75}{12}$

$\Rightarrow$ SP of 60 oranges $=60 \times \frac{75}{12}=₹ 375$

Here, CP of 60 oranges $>$ SP of 60 oranges.

Loss $=$ CP $-$ SP $=₹ 450-₹ 375=₹ 75$

$\therefore$ Loss $\%=\frac{\text { Loss }}{\text { CP }} \times 100 \%=\frac{75}{450} \times 100 \%=16 \frac{2}{3} \%$