Here is a simple descriptive statistics question.

When a student Joe, weighing 41 kg, joins a group of students whose average weight is 30 kg, the average weight goes up by 1 kg. Subsequently, if two students, excluding Joe, leave the group the average weight comes back to 30 kg. What is the difference between the average weight of the two students who left to the weight of Joe?

1. 11 kg

2. 5.5 kg

3. 71 kg

4. 36.5 kg

5. 30 kg

Oliver Diener says

5.5