Explanation:

- Gain Percent Calculation: A gain of 6 18/47% translates to a fractional value of 288/4700, meaning the dealer makes this profit by manipulating the weight.

- Understanding False Weight: When selling 1 kg, the correct method would utilize a weight of 1000 grams.

- Calculation Method: If the dealer indicates using a false weight, then to find this, divide 1000 grams by 1.0618 (since the gain is 6.18%).

- Numeric Resolution: By calculation, 1000 / 1.0618 ˜ 941.4 grams, indicating that he uses less than a kg to guarantee gain.

- Option Analysis:

- 953 grams: Too high to reach a 6.18% gain.

- 940 grams: Closest option to 941.4 grams.

- 960 grams: Higher than necessary for the specified profit.

- 947 grams: Still slightly high for the desired gain.

The correct answer is option 2: 940 grams.