Given : 5 True or False questions, no student has marked all correct answer and no 2 with same sequence of answers
To Find : Maximum number of students in class for this to be possible
Solution : From our given statement, it is evident that maximum possible number of correct answers = 4
Therefore,
Max number of students = Students with 0 correct answer + 1 correct answer + 2 correct answers + 3 correct answers + 4 correct answers
Since no 2 repeat sequence of correct answers, we need a unique sequence for each student.
0 correct answer --> Only 1 possibility (All Wrong) = Max 1 student (since sequence cannot repeat)
1 correct answer --> This can be chosen in 5C1 sequences = 5 students (one student per sequence)
2 correct answers --> This can be chosen in 5C2 sequences = 10 students (one student per sequence)
3 correct answers --> This can be chosen in 5C3 sequences = 10 students (one student per sequence)
4 correct answers --> This can be chosen in 5C4 sequences = 5 students (one student per sequence)
=> Max number of students = 1+5+10+10+5 = 31 students
Hence Option (B) is the right answer