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Logical Reasoning and Problem Solving
Directions: In a certain society, there are two marriage groups, Red and Brown. No marriage is permitted within a group. On marriage, males become part of their wife's group: women remain in their own group. Children belong to the same group as their parents. Widowers and divorced males revert to the group of their birth. Marriage to more than one person at the same time and marriage to a direct descendant are forbidden.
A Brown female could have had
I. a grandfather born Red
II. a grandmother born Red
III. two grandfathers born Brown
A Brown female stays Brown. Her father could be Red-born (married into Brown group). His father could be Red-born. So Brown female could have a Red-born grandfather (I) and Red-born grandmother (II). Two Brown grandfathers is impossible since at least one grandfather would be from outside group.