Logic Puzzle

Alright, let's tackle this problem step by step. I'll start by understanding the information given and then try to visualize the family structure to find out how many sisters Sally has.

Understanding the Problem

We have the following information:

1. Sally is a girl.
2. Sally has 3 brothers.
3. Each brother has 2 sisters.

The question is: How many sisters does Sally have?

At first glance, it might seem straightforward, but let's break it down to ensure we don't miss anything.

Identifying Family Members

First, let's list out the family members based on the information:

• Sally: She is a girl.
• Brothers: Sally has 3 brothers. Let's name them for clarity: Brother A, Brother B, and Brother C.

So far, the family consists of:

• Sally
• Brother A
• Brother B
• Brother C

Now, the next piece of information is that each brother has 2 sisters.

Analyzing "Each Brother Has 2 Sisters"

This is where we need to be careful. The statement says that each of Sally's brothers has 2 sisters.

Let's think about what this means for one brother, say Brother A:

• Brother A has 2 sisters.

Who could these sisters be?

We already know that Sally is a sister to Brother A because Sally is a girl and Brother A is her brother. So, one of Brother A's sisters is Sally.

But the statement says Brother A has 2 sisters, not just one. So, there must be another sister besides Sally.

This implies that there is another girl in the family who is a sister to Brother A.

Similarly, this would apply to Brother B and Brother C as well. Each of them has 2 sisters: one is Sally, and the other is this additional sister.

Determining the Additional Sister

From the above, we can deduce that there is another sister besides Sally.

Let's name this additional sister: Sister X.

Now, let's list all the siblings:

1. Sally
2. Sister X
3. Brother A
4. Brother B
5. Brother C

Now, let's verify the condition that each brother has 2 sisters:

• Brother A's sisters: Sally and Sister X → 2 sisters.
• Brother B's sisters: Sally and Sister X → 2 sisters.
• Brother C's sisters: Sally and Sister X → 2 sisters.

This checks out.

Counting Sally's Sisters

Now, the question is: How many sisters does Sally have?

From our list:

• Sally's siblings are: Sister X, Brother A, Brother B, Brother C.

Out of these, the sisters are Sister X.

So, Sally has 1 sister: Sister X.

Verifying the Answer

Let me double-check to ensure this makes sense.

• Total siblings: Sally, Sister X, Brother A, Brother B, Brother C → 5 children in total.
• Brothers: 3 (Brother A, B, C).
• Sisters: 2 (Sally and Sister X).

Now, for each brother:

• Number of sisters they have: 2 (Sally and Sister X).

This matches the given information that each brother has 2 sisters.

Now, for Sally:

• Her sisters: Only Sister X (since Sally is a girl, she doesn't count herself as her own sister).

Therefore, Sally has 1 sister.

Potential Missteps

Initially, one might think that since each brother has 2 sisters, and there are 3 brothers, the total number of sisters is 2 (as each brother's sisters are the same two girls).

But the key is to realize that Sally is one of those sisters, and the other sister is someone else.

Another way to look at it is:

• Total sisters in the family: Let's say S.
• We know Sally is one sister, so S ≥ 1.
• Each brother has 2 sisters, meaning S = 2 (since all brothers share the same sisters).
• Therefore, sisters are Sally and one other, making S = 2.
• Hence, Sally's sisters are the other sister, so 1.

Conclusion

After carefully analyzing the relationships and verifying the counts, it's clear that:

Sally has 1 sister.