Coffee costing Rs 250 per kg was mixed with chicory costing Rs 75 per kg in the ratio 5 : 2 for a certain blend.

Let $5 \mathrm{~kg}$ of coffee be mixed with $2 \mathrm{~kg}$ of chicory.

$\mathrm{CP}$ of the mixture $=\mathrm{Rs}(250 \times 5+75 \times 2)$

$=\mathrm{Rs}(1250+150)$

$=$ Rs. 1400

$\mathrm{SP}$ of the mixture $=\mathrm{Rs}(7 \times 230)=\mathrm{Rs} .1610$

Since SP $>\mathrm{CP}$, there is a gain.

Now, gain $=\operatorname{Rs}(1610-1400)$

$=$ Rs. 210

Gain percentage $=\left(\frac{\text { gain }}{\text { total } \mathrm{CP}} \times 100\right) \%$

$=\left(\frac{210}{1400} \times 100\right) \%$

$=15 \%$