There are two Classes A and B having 25 and 30 students respectively. In Class-A the highest score is 21 and lowest score is 17. In Class-B the highest score is 30 and lowest score is 22. Four students are shifted from Class-A to Class-B. Consider the following statements: 1. The average score of Class-B will definitely decrease. 2. The average score of Class-A will definitely increase. Which of the above statements is/are correct?

This is one of the easiest questions in this paper and could be solved mentally, check below - In case of averages, addition of items below average decreases it and adding items above average increases it. Lowest score of Class-B Student is higher than highest score of Class-A student. Therefore, any movement of student from A to B will lead to decrease in average. Hence, Statement 1 is correct. However, we don't know if marks of the 4 students that have been moved from class A are above or below the average. If above average, will lead to decrease in the average marks of Class A. If they have marks close to 17 ie below average, it will lead to increase in the average marks of Class A. Therefore, we cannot determine whether "definite" or confirmed increase happens. Hence, Statement 2 is incorrect.