The average cost price of two articles P and Q is Rs 1350. Article P sold at 10% profit and article Q sold at 20% profit. The total selling price of article P and Q is Rs 3120. If article Q is sold at 40% profit, then find the selling price.

Let's solve the problem step by step:

Step 1: Let's assume the cost price of article P is x and the cost price of article Q is y.

Step 2: We know that the average cost price of articles P and Q is Rs 1350. So, we can write the equation: (x + y) / 2 = 1350

Step 3: Simplifying the equation, we get: x + y = 2700

Step 4: We also know that the selling price of article P and Q is Rs 3120. So, we can write the equation: 1.1x + 1.2y = 3120 (since article P is sold at 10% profit and article Q is sold at 20% profit)

Step 5: Now, let's solve the system of equations formed by step 3 and step 4 to find the values of x and y.

Step 6: Multiplying the equation in step 3 by 1.1, we get: 1.1x + 1.1y = 2970

Step 7: Subtracting the equation in step 6 from the equation in step 4, we get: 1.2y - 1.1y = 3120 - 2970 0.1y = 150 y = 1500

Step 8: Substituting the value of y in the equation in step 3, we get: x + 1500 = 2700 x = 1200

Step 9: Now, we need to find the selling price of article Q when it is sold at 40% profit.

Step 10: The selling price of article Q with 40% profit can be calculated as: Selling price of Q = Cost price of Q + 40% of Cost price of Q Selling price of Q = 1500 + 0.4 * 1500 Selling price of Q = 1500 + 600 Selling price of Q = Rs 2100

Therefore, the selling price of article Q when it is sold at 40% profit is Rs 2100.