A trader mixes three varieties of groundnuts costing Rs. $50$, Rs. $20$ and Rs. $30$ per kg in the ratio $2:4:3$ in terms of weight and sells the mixture at Rs. $33$ per kg. What percentage of profit does he make?

Let the weights of the three varieties of groundnuts mixed be $2\text{kg}$, $4\text{kg}$, and $3\text{kg}$ respectively.
Total weight of the mixture $=2+4+3=9\text{kg}$.

Total cost price (CP) of the mixture:

$$\text{CP}=(2\times 50)+(4\times 20)+(3\times 30)=100+80+90=\text{Rs. }270$$

Selling price (SP) of the mixture per kg is Rs. $33$.
Total selling price (SP) of $9\text{kg}$ mixture:

$$\text{SP}=9\times 33=\text{Rs. }297$$

Profit made:

$$\text{Profit}=\text{SP}-\text{CP}=297-270=\text{Rs. }27$$

Profit percentage:

$$\text{Profit }\%=\left(\frac{\text{Profit}}{\text{CP}}\right)\times 100=\left(\frac{27}{270}\right)\times 100=10\%$$