Alright, let's tackle the problem step by step to ensure we understand it fully and arrive at the correct answer.

Problem Statement: Sally (a girl) has 3 brothers. Each brother has 2 sisters. How many sisters does Sally have?

Understanding the Problem: We need to determine the number of sisters Sally has, given the information about her brothers and their sisters.

Breaking It Down:

1. Sally's Brothers:

   • Sally has 3 brothers.

2. Brothers' Sisters:

   • Each brother has 2 sisters.

Key Point to Note: When it's mentioned that each brother has 2 sisters, it's important to recognize that Sally herself is one of those sisters.

Let's Visualize the Family:

• Total Brothers: 3
• Sisters per Brother: 2

Since Sally is one of the sisters, the total number of sisters includes her and possibly others.

Calculating the Number of Sisters:

Each of the 3 brothers has 2 sisters. Since Sally is one sister common to all brothers, we can determine how many additional sisters there are.

Let's denote:

• Total sisters = Number of sisters each brother has

But we know that Sally is one of those sisters. Therefore:

Total sisters = Sally + (Number of additional sisters)

Given that each brother has 2 sisters, and Sally is one of them, there must be one more sister.

So, Total sisters = 1 (Sally) + 1 (additional sister) = 2 sisters

Verification:

Let's verify this to ensure accuracy.

• Sally has 3 brothers.
• Each brother has 2 sisters: Sally and one more sister.
• Therefore, the total number of sisters is 2 (Sally and her sister).

This aligns with our calculation.

Common Pitfall:

A common mistake might be to think that since each brother has 2 sisters, and there are 3 brothers, there are 3 x 2 = 6 sisters. However, this overlooks the fact that Sally is the same sister for all brothers, so we're not adding unique sisters with each brother.

Conclusion:

After carefully analyzing the relationships and ensuring we account for Sally being one of the sisters, we conclude that Sally has 1 sister besides herself.

Final Answer: Sally has 1 sister.