A mobile phone was sold for Rs. 12, 600 after allowing a 10% discount on the marked price.

Let's solve this carefully step by step.

We are given:

• Selling Price (SP) = Rs. 12,600 (after 10% discount)

• Discount = 10% on Marked Price (MP)

• Profit = 20%

• We need the Cost Price (CP)

Step 1: Find the Marked Price (MP)

We know:

$ \text{SP} = \text{MP} \times \left(1 - \frac{\text{Discount %}}{100}\right) $

$ 12,600 = \text{MP} \times (1 - 0.1) $

$ 12,600 = \text{MP} \times 0.9 $

$ \text{MP} = \frac{12,600}{0.9} = 14,000 $

Step 2: Find the Cost Price (CP)

Profit = 20%, so:

$ \text{SP} = \text{CP} \times \left(1 + \frac{\text{Profit %}}{100}\right) $

$ 12,600 = \text{CP} \times 1.2 $

$ \text{CP} = \frac{12,600}{1.2} = 10,500 $

Answer: Rs. 10,500