A shopkeeper sells his goods at cost price but uses a weight of 970 grams for…

Step-by-Step Solution

To calculate the gain percentage when a shopkeeper uses a faulty weight, we compare the actual amount sold to the amount the customer thinks they are receiving.

1. Understand the situation:

   • The shopkeeper claims to sell 1 kg (1000 grams) of goods.

   • In reality, they are only giving 970 grams.

   • Since they sell at the cost price (CP), we can assume the cost price of 1 gram is Re 1.

   • Therefore, the cost price (CP) of the 970 grams actually sold is Rs 970.

   • The shopkeeper receives the money for 1000 grams, so the selling price (SP) is Rs 1000.

2. Calculate the profit:

   • Profit = SP - CP

   • Profit = 1000 - 970 = 30

3. Calculate the gain percentage:

   • Gain % = (Profit / CP) * 100

   • Gain % = (30 / 970) * 100

   • Gain % = 3000 / 970 ≈ 3.0927...%