Logic Puzzle

To determine how many sisters Sally has, let's analyze the family structure step by step.

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Step 1: Understand the Given Information

• Sally is a girl.
• She has 3 brothers.
  → This means there are 3 boys in the family (excluding Sally).
• Each brother has 2 sisters.

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Step 2: Analyze the Brothers' Perspective

Each of Sally’s 3 brothers has 2 sisters. Since Sally is one of those sisters (she's a girl), that implies:

• There must be one more sister besides Sally.
• So, the total number of girls in the family = Sally + 1 other girl = 2 girls.

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Step 3: Determine How Many Sisters Sally Has

• Sally is one of the two girls in the family.
• Therefore, she has 1 sister (the other girl).

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Final Answer

$$ \boxed{1} $$