A vendor purchased bananas at ₹ 40 per dozen and sold them at 10 for ₹ 36.

LCM of 12 and $10=60$

Let the number of banana bought be $60 .$

CP of 12 banana $=₹ 40$

$\therefore$ CP of 1 banana $=\frac{40}{12}=₹ \frac{10}{3}$

$\Rightarrow$ CP of 60 bananas $=60 \times \frac{10}{3}=₹ 200$

SP of 10 bananas $=₹ 36$

$\therefore$ SP of 1 banana $=\frac{36}{10}=₹ \frac{18}{5}$

$\Rightarrow$ SP of 60 bananas $=60 \times \frac{18}{5}=₹ 216$

Here, SP of 60 bananas $>\mathrm{CP}$ of 60 bananas.

Profit $=\mathrm{SP}-\mathrm{CP}=₹ 216-₹ 200=₹ 16$

$\therefore$ Profit\% $=\frac{\text { Profit }}{\mathrm{CP}} \times 100 \%=\frac{16}{200} \times 100=8 \%$