Because grouping questions partition elements into sets, the number of elements is often an issue. As
mentioned before, counting can be challenging. This tends to make grouping questions more difficult than
ordering questions.
Pay close attention to the maximum or minimum number of elements in a group; this is often the heart
of the question.
Grouping questions can be classified as those that partition the elements into 2 groups, and those that
partition the elements into 3 or more groups. The former are sometimes called selection questions because
they “select” elements from a pool, dividing the pool into two groups: those selected and those not selected.
Points to Remember
- Pay close attention to the maximum or minimum number of elements in a group, for this is often the
heart of the game.
- Grouping questions are classified as those that divide the elements into two sets—Selection questions—and
those that divide the elements into three or more sets.
- A reciprocal condition affects both elements equally.
- Don’t interpret a nonreciprocal condition as reciprocal.
- The method of indirect proof is used often with grouping questions.