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In a class, there are 100 students. Of them, 60 students attend music classes, 40 students attend dance classes, and 20 students attend both the classes. Find the number of students who attend neither of the classes. The following steps are involved in solving the above problem. Arrange them in sequential order (A) n(M cup D)=n(M)+n(D)-n(M cup D) rarr n(M cap D)rarr n(M cup D)=60 + 40 -20 =100 -20 = 80 ( B) therefore Number of students who attend neither of the classes = 100 - 80 = 20 ( C) n(M)=60 ,n(D)=40 and n(M cap D)= 20 ("given") (D) Let n(M) be the number of students who attend music classes and n(D) be the number of students who attend dance classes.

In a class there were 28 boys and some girls. In a test the mean score obtained by the boys was 12.5 while that obtained by the girls was 14.5. If the overall average was 13.1. what was the total number of students in the class?

The average of 80 boys in a class is 15. The average age of a group of 15 boys in the class is 16 and the average age of another 25 boys in the class is 14. What is the average age of the remaining boys in the class? (a) 14 (b) 14.75 (c) 15.25 (d) Cannot be determined (e) None of these