Two teachers cheat with grades!
Class 9b consists of 25 pupils, there is 1 people who got a 5, and for every grade left, namely 1,2,3 and 4 are 6 pupils. Therefore the average of their grades is 2.6
Now their teachers want to improve the grades of both classes by making 2 or 3 pupils switch from class 9b to 9a.
Now how many possible groups of 2 and 3 pupils from class 9b can be formed, so that the average grade of both classes improve?
Note: 1 is the best possible grade, grade 6 the worst. Therefore an average grade of 3.0 for Class 9a would be an improvement. Possible grades are the integers: 1,2,3,4,5,6