Three Students and One Teacher Puzzle

Interview Puzzle

There are three students and one teacher the teacher ask a question and student give answer for that question if answer is correct then only he allow to enter in class.
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Teacher:12 ?
1st student: 6
Teacher:come in

Teacher:6 ?
2nd student: 3
Teacher:come in

Teacher:10 ?
3rd student: 5
Teacher:wrong, don't come!!!!!!!!!!
what should be the answer of 3rd student to enter in class?
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Answer:-   3

 12: twelve = 6(letters) ,
  6:six= 3 (letters) so, 
 10:ten= 3
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