Logic Puzzle

To determine how many sisters Sally has, let's analyze the information step by step:

1. Sally is a girl, and she has 3 brothers.
   This means there are 3 boys in the family (her brothers).

2. Each brother has 2 sisters.
   From the perspective of any one brother, he sees 2 girls in the family.
   Since Sally is one of the girls, there must be one more girl besides Sally to make up the 2 sisters each brother counts.

3. Total number of girls in the family:

   • Sally (1 girl)
   • The other sister (1 girl)
     Total = 2 girls

4. How many sisters does Sally have?
   Sally herself is one of the girls, so the number of sisters she has is the other girl(s).
   Since there are 2 girls total and Sally is one, she has 1 sister.

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Answer: Sally has 1 sister.