A medium difficulty GMAT problem solving practice question in averages and statistics. A 650 level question. Word problem in averages.
Concept: Computing average after addition of members and after removing members to a group.
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 and the weight of Joe?
A. 11 kg
B. 5.5 kg
C. 71 kg
D. 36.5 kg
E. 30 kg
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