Logic Puzzle

Sally has 3 brothers, meaning there are 3 boys in the family. Each brother has 2 sisters, indicating that there are exactly 2 girls in the family. Since Sally is one of the girls, there must be one additional sister. Therefore, Sally has one sister.

This can be verified by considering the family composition:

• Sisters: Sally and one other girl.
• Brothers: 3 boys.

From Sally's perspective:

• She has 3 brothers.
• She has 1 sister (the other girl).

From each brother's perspective:

• They have 2 sisters (Sally and the other girl).

This satisfies both conditions: Sally has 3 brothers, and each brother has 2 sisters.

If there were only one sister (Sally), then each brother would have only one sister, which contradicts the information that each brother has 2 sisters. If there were three sisters, then each brother would have three sisters, which also contradicts the information that each brother has 2 sisters. Thus, there must be exactly two sisters, meaning Sally has one sister.

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