There are 42 students in class 6 (1). The number of students in class 6 (2) is 20 / 21 of that in class 6 (1). The number of students in class 6 (3) is ten times more than that in class 6 (2)

There are 42 students in class 6 (1). The number of students in class 6 (2) is 20 / 21 of that in class 6 (1). The number of students in class 6 (3) is ten times more than that in class 6 (2)

There are 42 students in class 6 (2) = 40
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