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The question is followed by two statements I and II.

Mark

1. if the question can be answered by any one of the statements alone, but cannot be answered by using the other statement alone.
2. if the question can be answered by using either statement alone.
3. if the question can be answered by using both the statements together, but cannot be answered by using either statement alone.
4. if the question cannot be answered even by using both the statements together.

The average weight of students in a class is $50 \; \text{kg}.$ What is the number of students in the class?

1. The heaviest and the lightest members of the class weigh $60 \; \text{kg}$ and $40 \; \text{kg}$ respectively.
2. Exclusion of the heaviest and the lightest members from the class does not change the average weight of the students.

Heaviest member of the class weight $= 60 \; \text{kg}$

lightest member of the class weight $= 40 \; \text{kg}$

Avg weight $= 50 \; \text{kg}$

But Avg weight can be formed from only that two students too

So, we cannot conclude number of students in the class

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