A coffee merchant buys 30 kg of dark roast beans at Rs. 120 per kg and 70 kg of light roast beans at Rs. 160 per kg. He blends both varieties together and sells the entire mixture at Rs. 150 per kg. Determine his overall profit or loss.

The correct answer is Rs. 200 profit.

Step 1: Calculate the total Cost Price (CP) of the coffee beans.

Cost of 30 kg dark roast beans = 30 × 120 = Rs. 3600
Cost of 70 kg light roast beans = 70 × 160 = Rs. 11200

$\text{Total CP}=3600+11200=\text{Rs.}14800$

Step 2: Calculate the total Selling Price (SP) of the mixture.

Total weight of the mixture = 30 kg + 70 kg = 100 kg
Selling price per kg = Rs. 150

$\text{Total SP}=100\times 150=\text{Rs.}15000$

Step 3: Calculate the overall profit or loss.

Since the total Selling Price (SP) is greater than the total Cost Price (CP), the merchant makes a profit.

$\text{Profit}=\text{Total SP}-\text{Total CP}$

$\text{Profit}=15000-14800=\text{Rs.}200$

Therefore, the merchant earns an overall profit of Rs. 200 profit.