To clarify the question, you're asking about the possibility of getting 20 bags from a multibag pack where each individual bag weighs 12 grams, with variations between 11 and 13 grams (from -1 gm to +2 gm).

This can be interpreted as a situation involving random variations in the bag weight, but we need to narrow down how you want the probability calculated. Here's what I can infer:

1. Weight Range: Each bag's weight is between 11 and 13 grams. So, the possible weight for each bag could be either:

   • 11 grams
   • 12 grams
   • 13 grams

2. Total Weight Calculation: You want the total weight of 20 bags. Let's calculate the possible total weights based on the variations in individual bag weights.

For 20 bags:

• The minimum weight would be if all the bags weighed 11 grams:
  $20 \times 11 = 220 \text{ grams}$

• The maximum weight would be if all the bags weighed 13 grams:
  $20 \times 13 = 260 \text{ grams}$

• The average weight would be if all the bags weighed 12 grams:
  $20 \times 12 = 240 \text{ grams}$

Possibility Calculation (Probability Distribution)

To calculate the exact probability of getting exactly 20 bags with some specific total weight, we would typically consider:

• How many bags are likely to weigh 11, 12, or 13 grams.
• The distribution and likelihood for each bag's weight.

This would involve calculating probabilities assuming a uniform distribution (equal likelihood for each of 11, 12, or 13 grams), or if you have more specific distribution information (e.g., a normal distribution), we could model that as well.

Would you like to dive deeper into a specific aspect (e.g., the distribution of bags) or want a more exact calculation based on assumptions?